U.S. patent application number 16/680152 was filed with the patent office on 2020-08-13 for carbon-lead blends for use in hybrid energy storage devices.
The applicant listed for this patent is BASF SE. Invention is credited to Alan Tzu-Yang CHANG, Henry R. COSTANTINO, Aaron M. FEAVER, Katharine GERAMITA, Matthew J. MAROON, Avery SAKSHAUG, Leah A. THOMPKINS.
Application Number | 20200259181 16/680152 |
Document ID | 20200259181 / US20200259181 |
Family ID | 1000004786372 |
Filed Date | 2020-08-13 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200259181 |
Kind Code |
A1 |
THOMPKINS; Leah A. ; et
al. |
August 13, 2020 |
CARBON-LEAD BLENDS FOR USE IN HYBRID ENERGY STORAGE DEVICES
Abstract
The present application is directed to blends comprising a
plurality of carbon particles and a plurality of lead particles.
The blends find utility in any number of electrical devices, for
example, in lead acid batteries. Methods for making and using the
blends are also disclosed.
Inventors: |
THOMPKINS; Leah A.;
(Seattle, WA) ; FEAVER; Aaron M.; (Seattle,
WA) ; COSTANTINO; Henry R.; (Woodinville, WA)
; CHANG; Alan Tzu-Yang; (Renton, WA) ; GERAMITA;
Katharine; (Seattle, WA) ; SAKSHAUG; Avery;
(Everett, WA) ; MAROON; Matthew J.; (Peoria,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafen |
|
DE |
|
|
Family ID: |
1000004786372 |
Appl. No.: |
16/680152 |
Filed: |
November 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13486731 |
Jun 1, 2012 |
10522836 |
|
|
16680152 |
|
|
|
|
61493350 |
Jun 3, 2011 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/14 20130101; Y02T
10/70 20130101; H01M 4/583 20130101; Y02E 60/13 20130101; H01B 1/04
20130101; H01M 4/625 20130101; H01B 1/02 20130101; H01B 1/18
20130101; C08K 3/04 20130101; H01G 11/50 20130101; C08K 3/08
20130101; Y02E 60/10 20130101; C08K 7/22 20130101; H01M 10/06
20130101; H01M 4/56 20130101; H01M 2004/021 20130101 |
International
Class: |
H01M 4/62 20060101
H01M004/62; H01M 4/14 20060101 H01M004/14; H01M 4/56 20060101
H01M004/56; H01G 11/50 20060101 H01G011/50; H01M 4/583 20060101
H01M004/583; H01B 1/18 20060101 H01B001/18; C08K 7/22 20060101
C08K007/22; C08K 3/08 20060101 C08K003/08; C08K 3/04 20060101
C08K003/04 |
Claims
1. (canceled)
2. A blend comprising a plurality of carbon particles and a
plurality of lead particles, wherein the carbon particles comprise
lead within a pore structure or on a surface of the carbon
particles.
3. A blend comprising a plurality of carbon particles and a
plurality of lead particles.
4. The blend of claim 3, wherein the blend comprises a total of
less than 500 PPM of elements having atomic numbers ranging from 11
to 92, excluding lead, as measured by proton induced x-ray
emission.
5-9. (canceled)
10. The blend of claim 3, wherein the lead is in elemental form or
in the form of lead (II) oxide, lead (IV) oxide, lead acetate, lead
carbonate, lead sulfate, lead orthoarsenate, lead pyroarsenate,
lead bromide, lead caprate, lead carproate, lead caprylate, lead
chlorate, lead chloride, lead fluoride, lead nitrate, lead
oxychloride, lead orthophosphate sulfate, lead chromate, lead
chromate, basic, lead ferrite, lead sulfide, lead tungstate or
combinations thereof.
11-12. (canceled)
13. The blend of claim 3, wherein the mass percent of carbon
particles as a percentage of the total mass of carbon particles and
lead particles ranges from 0.1% to 50%.
14. (canceled)
15. The blend of claim 3, wherein the volume percent of carbon
particles as a percentage of the total volume of carbon particles
and lead ranges from 0.1% to 50%.
16-17. (canceled)
18. The blend of claim 3, wherein the surface area percent of
carbon particles as a percentage of the total surface area of
carbon particles and lead particles ranges from 0.1% to 50%.
19. The blend of claim 3, wherein the carbon particle surface area
residing in pores less than 20 angstroms as a percentage of the
total surface area residing in pores less than 20 angstroms of
carbon particles and lead particles ranges from 20% to 60%.
20. (canceled)
21. The blend of claim 3, wherein the volume average particle size
of carbon particles relative to the volume average particle size of
lead particles ranges from 0.01:1 to 100:1.
22-33. (canceled)
34. The blend of claim 4, wherein the carbon particles comprise
less than 5 ppm chromium, less than 10 ppm iron, less than 5 ppm
nickel, less than 20 ppm silicon, less than 5 ppm zinc, and
bismuth, silver, copper, mercury, manganese, platinum, antimony and
tin are not detected as measured by proton induced x-ray
emission.
35-42. (canceled)
43. The blend of claim 3, wherein the carbon particles comprise a
BET specific surface area of at least 1000 m.sup.2/g.
44-47. (canceled)
48. The blend of claim 3, wherein the carbon particles comprise a
total pore volume of at least 0.5 cc/g.
49. The blend of claim 3, wherein the carbon particles comprise a
DFT pore volume of at least 0.25 cc/g for pores less than 20
angstroms.
50. The blend of claim 3, wherein the carbon particles comprise a
DFT pore volume of at least 0.75 cc/g for pores greater than 20
angstroms.
51-55. (canceled)
56. The blend of claim 3, wherein the carbon particles comprise a
pore volume ranging from 0.4 cc/g to 1.4 cc/g and an R factor of
0.2 or less at relative humidities ranging from about 10% to
100%.
57-64. (canceled)
65. The blend of claim 3, wherein the carbon particles are
acidic.
66. (canceled)
67. The blend of claim 3, wherein the carbon particles are
basic.
68. An electrical energy storage device comprising a blend of claim
3.
69-73. (canceled)
74. An electrode comprising a binder and a blend of claim 3.
75-82. (canceled)
83. A composition comprising the blend of claim 3 and an
electrolyte.
84-93. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of U.S.
patent application Ser. No. 13/486,731, filed Jun. 1, 2012, which
claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S.
Provisional Patent Application No. 61/493,350, filed Jun. 3, 2011,
each of which is incorporated herein by reference in its
entirety.
BACKGROUND
Technical Field
[0002] The present application relates to compositions and devices
for energy storage and distribution. The compositions comprise a
plurality of lead particles and a plurality of carbon particles and
exhibit desirable electrochemical properties suitable for use in
hybrid carbon-lead energy storage devices.
Description of the Related Art
[0003] Hybrid energy storage devices, also known as asymmetric
supercapacitors or hybrid battery/supercapacitors, utilize a
combination of battery electrodes and supercapacitor electrodes.
For example, hybrid lead-carbon energy storage devices employ
lead-acid battery positive electrodes (cathodes) and ultracapacitor
negative electrodes (anodes). Such devices comprise a unique set of
characteristics including long cycle life, increased power, fast
recharge capability and a wide range of temperature operability.
Conventional lead-acid energy storage devices may have limited
active life and power performance. Hybrid energy storage devices
employing either carbon or lead-acid electrodes (but not their
combination at the same electrode) may provide some improvement and
advantages over conventional lead-acid devices; however, their
active life, energy capacity and power performance can likewise be
limited. For example, lead-based positive electrodes often fail due
to a loss of active lead dioxide paste from the current collector
grid after multiple charge/discharge cycles. The anodes of these
devices also deteriorate upon multiple charge/discharge cycles
because the discharge lead sulfate crystal size increases and leads
to `densification` of the negative plate resulting in reduced
charge acceptance and loss of capacity. This electrode failure is
thought to be a result of secondary and tertiary side reactions
caused by impurities in the carbon materials employed in these
devices. In addition, the low surface area of the electrodes and
relatively high ion migration distances limits the power
performance of these devices.
[0004] The conventional wisdom is that such energy storage devices,
particularly those made in commercial quantities require
significant compression of the electrodes as they are placed into
the case for the energy storage device. Moreover, because
supercapacitor energy storage devices of the sort discussed herein
comprise lead-based positive electrodes together with carbon-based
negative electrodes, and lead-based positive electrodes are known
from the lead acid battery art, considerable attention has been
paid to the development of improved negative electrodes.
[0005] The positive electrode of ultracapacitor energy storage
devices effectively defines the active life of the device. The
negative electrodes typically will not wear out; but on the other
hand, just as with lead acid storage batteries, the positive
lead-based electrodes of ultracapacitor energy storage devices will
typically fail first. Those failures are generally the result of
the loss of active lead dioxide paste shedding from the current
collector grid as a consequence of spalling and dimensional change
deterioration during charging and discharging cycles.
[0006] Although the need for improved carbon materials for use in
hybrid lead-carbon energy storage devices has been recognized, such
carbon material has yet to be developed. Accordingly, there
continues to be a need in the art for improved electrode materials
for use in hybrid lead-carbon electrical energy storage devices, as
well as for methods of making the same and devices containing the
same. The present invention fulfills these needs and provides
further related advantages.
BRIEF SUMMARY
[0007] In general terms, the current invention is directed to
compositions and devices for energy storage and distribution that
employ a physical blend of carbon particles and lead particles.
These blends of lead with the carbon materials exhibit desirable
electrochemical properties suitable for use in hybrid carbon-lead
energy storage devices. The carbon particles may be any suitable
carbon material. For example, in some embodiments the carbon
particles are activated carbon particles, and in other embodiments
the carbon particles are ultrapure. In other embodiments the carbon
particles comprise a total PUCE impurity content of greater than
1000 PPM (i.e., "non-ultrapure"). The carbon material may also
comprise certain additives. For example, in some embodiments the
carbon particles comprise a lead material (e.g., lead oxide)
impregnated within the pores of the carbon or on the surface of the
carbon.
[0008] Accordingly, in one embodiment the present invention
provides a blend comprising a plurality of carbon particles and a
plurality of lead particles In other embodiments, the invention
provides a blend comprising carbon and lead, wherein the blend
comprises a total impurity content of less than 500 ppm of all
elements having atomic numbers ranging from 11 to 92, excluding
lead, as measured by proton induced x-ray emission.
[0009] In another embodiment, the invention is directed to a blend
comprising a plurality of carbon particles and a plurality of lead
particles, wherein the carbon particles comprise lead within a pore
structure or on a surface of the carbon particles.
[0010] In still other embodiments, the invention provides an
electrical energy storage device comprising any of the blends
disclosed herein. For example, in some embodiments the device is a
battery comprising:
[0011] a) at least one positive electrode comprising a first active
material in electrical contact with a first current collector;
[0012] b) at least one negative electrode comprising a second
active material in electrical contact with a second current
collector; and
[0013] c) an electrolyte;
[0014] wherein the positive electrode and the negative electrode
are separated by an inert porous separator, and wherein at least
one of the first or second active materials comprises a blend
according to the present disclosure.
[0015] Negative active materials comprising the carbon-lead blends
are also provided. Furthermore, energy storage devices comprising
the negative active material are also provided. In addition,
methods of using the novel compositions and devices are also
provided.
[0016] These and other aspects of the invention will be apparent
upon reference to the following detailed description. To this end,
various references are set forth herein which describe in more
detail certain background information, procedures, compounds and/or
compositions, and are each hereby incorporated by reference in
their entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In the figures, identical reference numbers identify similar
elements. The sizes and relative positions of elements in the
figures are not necessarily drawn to scale and some of these
elements are arbitrarily enlarged and positioned to improve figure
legibility. Further, the particular shapes of the elements as drawn
are not intended to convey any information regarding the actual
shape of the particular elements, and have been solely selected for
ease of recognition in the figures.
[0018] FIG. 1 depicts a representation of an exemplary energy
storage device.
[0019] FIG. 2 presents carbon capacitance of different carbon
samples.
[0020] FIG. 3 shows a nitrogen sorption isotherm for microporous
activated carbon.
[0021] FIG. 4 presents a DFT pore volume distribution for
microporous carbon.
[0022] FIG. 5 depicts a DFT pore volume distribution for mesoporous
activated carbon.
[0023] FIG. 6 shows the DFT pore volume distribution for mesoporous
carbon before (open circles) and after (solid diamonds)
impregnation with lead acetate.
[0024] FIG. 7 is a pore size distribution for a mesoporous carbon
material.
[0025] FIG. 8 shows carbon mass as a function of coating volume for
a carbon coated lead electrode.
[0026] FIG. 9 is a plot showing water uptake for activated and
unactivated carbons having various pore volumes.
[0027] FIG. 10 displays water weight gain of different carbon
particles.
[0028] FIG. 11 shows the relationship between surface area and
gravimetric capacitance for various carbon samples.
[0029] FIG. 12 is a graph showing capacitance and specific surface
area of carbon-lead blends.
[0030] FIG. 13 depicts the relationship of the density of pastes
comprising carbon-lead blends and the ratio of solvent to solid in
the pastes.
[0031] FIG. 14 shows wettability of different carbon samples.
[0032] FIG. 15 is a plot showing incremental pore volume of
different carbon samples.
[0033] FIG. 16 illustrates the change in the molarity of a sulfuric
acid solution versus the pH of activated and pre-actived carbon
samples.
DETAILED DESCRIPTION
[0034] In the following description, certain specific details are
set forth in order to provide a thorough understanding of various
embodiments. However, one skilled in the art will understand that
the invention may be practiced without these details. In other
instances, well-known structures have not been shown or described
in detail to avoid unnecessarily obscuring descriptions of the
embodiments. Unless the context requires otherwise, throughout the
specification and claims which follow, the word "comprise" and
variations thereof, such as, "comprises" and "comprising" are to be
construed in an open, inclusive sense, that is, as "including, but
not limited to." Further, headings provided herein are for
convenience only and do not interpret the scope or meaning of the
claimed invention.
[0035] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment. Thus, the appearances of the
phrases "in one embodiment" or "in an embodiment" in various places
throughout this specification are not necessarily all referring to
the same embodiment. Furthermore, the particular features,
structures, or characteristics may be combined in any suitable
manner in one or more embodiments. Also, as used in this
specification and the appended claims, the singular forms "a,"
"an," and "the" include plural referents unless the content clearly
dictates otherwise. It should also be noted that the term "or" is
generally employed in its sense including "and/or" unless the
content clearly dictates otherwise.
Definitions
[0036] As used herein, and unless the context dictates otherwise,
the following terms have the meanings as specified below.
[0037] "Carbon material" refers to a material or substance
comprised substantially of carbon. Carbon materials include
ultrapure as well as amorphous and crystalline carbon materials.
Examples of carbon materials include, but are not limited to,
activated carbon, pyrolyzed dried polymer gels, pyrolyzed polymer
cryogels, pyrolyzed polymer xerogels, pyrolyzed polymer aerogels,
activated dried polymer gels, activated polymer cryogels, activated
polymer xerogels, activated polymer aerogels and the like.
[0038] "Amorphous" refers to a material, for example an amorphous
carbon material, whose constituent atoms, molecules, or ions are
arranged randomly without a regular repeating pattern. Amorphous
materials may have some localized crystallinity (i.e., regularity)
but lack long-range order of the positions of the atoms. Pyrolyzed
and/or activated carbon materials are generally amorphous.
[0039] "Crystalline" refers to a material whose constituent atoms,
molecules, or ions are arranged in an orderly repeating pattern.
Examples of crystalline carbon materials include, but are not
limited to, diamond and graphene.
[0040] "Synthetic" refers to a substance which has been prepared by
chemical means rather than from a natural source. For example, a
synthetic carbon material is one which is synthesized from
precursor materials and is not isolated from natural sources.
[0041] "Impurity" or "impurity element" refers to an undesired
foreign substance (e.g., a chemical element) within a material
which differs from the chemical composition of the base material.
For example, an impurity in a carbon material refers to any element
or combination of elements, other than carbon, which is present in
the carbon material. Impurity levels are typically expressed in
parts per million (ppm).
[0042] "PIXE impurity" or "PIXE element" is any impurity element
having an atomic number ranging from 11 to 92 (i.e., from sodium to
uranium). The phrases "total PIXE impurity content" and "total PIXE
impurity level" both refer to the sum of all PIXE impurities
present in a sample, for example, a polymer gel or a carbon
material. Electrochemical modifiers are not considered PIXE
impurities as they are a desired constituent of the carbon
materials. For example, in some embodiments an element may be
intentionally added to a carbon material, for example lead, and
will not be considered a PIXE impurity, while in other embodiments
the same element may not be desired and, if present in the carbon
material, will be considered a PIXE impurity. PIXE impurity
concentrations and identities may be determined by proton induced
x-ray emission (PIXE).
[0043] "Ultrapure" refers to a substance having a total PIXE
impurity content of less than 0.010%. For example, an "ultrapure
carbon material" is a carbon material having a total PIXE impurity
content of less than 0.010% (i.e., 1000 ppm).
[0044] "Ash content" refers to the nonvolatile inorganic matter
which remains after subjecting a substance to a high decomposition
temperature. Herein, the ash content of a carbon material is
calculated from the total PIXE impurity content as measured by
proton induced x-ray emission, assuming that nonvolatile elements
are completely converted to expected combustion products (i.e.,
oxides).
[0045] "Polymer" refers to a macromolecule comprised of two or more
structural repeating units.
[0046] "Synthetic polymer precursor material" or "polymer
precursor" refers to compounds used in the preparation of a
synthetic polymer. Examples of polymer precursors that can be used
in certain embodiments of the preparations disclosed herein
include, but are not limited to, aldehydes (i.e., HC(.dbd.O)R,
where R is an organic group), such as for example, methanal
(formaldehyde); ethanal (acetaldehyde); propanal (propionaldehyde);
butanal (butyraldehyde); glucose; benzaldehyde and cinnamaldehyde.
Other exemplary polymer precursors include, but are not limited to,
phenolic compounds such as phenol and polyhydroxy benzenes, such as
dihydroxy or trihydroxy benzenes, for example, resorcinol (i.e.,
1,3-dihydroxy benzene), catechol, hydroquinone, and phloroglucinol.
Mixtures of two or more polyhydroxy benzenes are also contemplated
within the meaning of polymer precursor.
[0047] "Monolithic" refers to a solid, three-dimensional structure
that is not particulate in nature.
[0048] "Sol" refers to a colloidal suspension of precursor
particles (e.g., polymer precursors), and the term "gel" refers to
a wet three-dimensional porous network obtained by condensation or
reaction of the precursor particles.
[0049] "Polymer gel" refers to a gel in which the network component
is a polymer; generally a polymer gel is a wet (aqueous or
non-aqueous based) three-dimensional structure comprised of a
polymer formed from synthetic precursors or polymer precursors.
[0050] "Sol gel" refers to a sub-class of polymer gel where the
polymer is a colloidal suspension that forms a wet
three-dimensional porous network obtained by reaction of the
polymer precursors.
[0051] "Polymer hydrogel" or "hydrogel" refers to a subclass of
polymer gel or gel wherein the solvent for the synthetic precursors
or monomers is water or mixtures of water and one or more
water-miscible solvent.
[0052] "Carbon hydrogel" refers to a sub-class of a hydrogel
wherein the synthetic polymer precursors are largely organic in
nature.
[0053] "RF polymer hydrogel" refers to a sub-class of polymer gel
wherein the polymer was formed from the catalyzed reaction of
resorcinol and formaldehyde in water or mixtures of water and one
or more water-miscible solvent.
[0054] "Acid" refers to any substance that is capable of lowering
the pH of a solution. Acids include Arrhenius, Bronsted and Lewis
acids. A "solid acid" refers to a dried or granular compound that
yields an acidic solution when dissolved in a solvent. The term
"acidic" means having the properties of an acid.
[0055] "Base" refers to any substance that is capable of raising
the pH of a solution. Bases include Arrhenius, Bronsted and Lewis
bases. A "solid base" refers to a dried or granular compound that
yields basic solution when dissolved in a solvent. The term "basic"
means having the properties of a base.
[0056] "Mixed solvent system" refers to a solvent system comprised
of two or more solvents, for example, two or more miscible
solvents. Examples of binary solvent systems (i.e., containing two
solvents) include, but are not limited to: water and acetic acid;
water and formic acid; water and propionic acid; water and butyric
acid and the like. Examples of ternary solvent systems (i.e.,
containing three solvents) include, but are not limited to: water,
acetic acid, and ethanol; water, acetic acid and acetone; water,
acetic acid, and formic acid; water, acetic acid, and propionic
acid; and the like. The present invention contemplates all mixed
solvent systems comprising two or more solvents.
[0057] "Miscible" refers to the property of a mixture wherein the
mixture forms a single phase over certain ranges of temperature,
pressure, and composition.
[0058] "Catalyst" is a substance which alters the rate of a
chemical reaction. Catalysts participate in a reaction in a cyclic
fashion such that the catalyst is cyclically regenerated. The
present disclosure contemplates catalysts which are sodium free.
The catalyst used in the preparation of a ultrapure polymer gel as
described herein can be any compound that facilitates the
polymerization of the polymer precursors to form an ultrapure
polymer gel. A "volatile catalyst" is a catalyst which has a
tendency to vaporize at or below atmospheric pressure. Exemplary
volatile catalysts include, but are not limited to, ammoniums
salts, such as ammonium bicarbonate, ammonium carbonate, ammonium
hydroxide, and combinations thereof. Generally such catalysts are
used in the range of molar ratios of 10:1 to 2000:1 phenolic
compound:catalyst. Typically, such catalysts can be used in the
range of molar ratios of 20:1 to 200:1 phenolic compound:catalyst.
For example, such catalysts can be used in the range of molar
ratios of 25:1 to 100:1 phenolic compound:catalyst.
[0059] "Solvent" refers to a substance which dissolves or suspends
reactants (e.g., ultrapure polymer precursors) and provides a
medium in which a reaction may occur. Examples of solvents useful
in the preparation of the gels, ultrapure polymer gels, ultrapure
synthetic carbon materials and ultrapure synthetic amorphous carbon
materials disclosed herein include, but are not limited to, water,
alcohols and mixtures thereof. Exemplary alcohols include ethanol,
t-butanol, methanol and mixtures thereof. Such solvents are useful
for dissolution of the synthetic ultrapure polymer precursor
materials, for example dissolution of a phenolic or aldehyde
compound. In addition, in some processes such solvents are employed
for solvent exchange in a polymer hydrogel (prior to freezing and
drying), wherein the solvent from the polymerization of the
precursors, for example, resorcinol and formaldehyde, is exchanged
for a pure alcohol. In one embodiment of the present application, a
cryogel is prepared by a process that does not include solvent
exchange.
[0060] "Dried gel" or "dried polymer gel" refers to a gel or
polymer gel, respectively, from which the solvent, generally water,
or mixture of water and one or more water-miscible solvents, has
been substantially removed.
[0061] "Pyrolyzed dried polymer gel" refers to a dried polymer gel
which has been pyrolyzed but not yet activated, while an "activated
dried polymer gel" refers to a dried polymer gel which has been
activated.
[0062] "Cryogel" refers to a dried gel that has been dried by
freeze drying.
[0063] "RF cryogel" refers to a dried gel that has been dried by
freeze drying wherein the gel was formed from the catalyzed
reaction of resorcinol and formaldehyde.
[0064] "Pyrolyzed cryogel" is a cryogel that has been pyrolyzed but
not yet activated.
[0065] "Activated cryogel" is a cryogel which has been activated to
obtain activated carbon material.
[0066] "Xerogel" refers to a dried gel that has been dried by air
drying, for example, at or below atmospheric pressure.
[0067] "Pyrolyzed xerogel" is a xerogel that has been pyrolyzed but
not yet activated.
[0068] "Activated xerogel" is a xerogel which has been activated to
obtain activated carbon material.
[0069] "Aerogel" refers to a dried gel that has been dried by
supercritical drying, for example, using supercritical carbon
dioxide.
[0070] "Pyrolyzed aerogel" is an aerogel that has been pyrolyzed
but not yet activated.
[0071] "Activated aerogel" is an aerogel which has been activated
to obtain activated carbon material.
[0072] "Activate" and "activation" each refer to the process of
heating a raw material or carbonized/pyrolyzed substance at an
activation dwell temperature during exposure to oxidizing
atmospheres (e.g., carbon dioxide, oxygen, steam or combinations
thereof) to produce an "activated" substance (e.g., activated
cryogel or activated carbon material). The activation process
generally results in a stripping away of the surface of the
particles, resulting in an increased surface area. Alternatively,
activation can be accomplished by chemical means, for example, by
impregnation of carbon-containing precursor materials with
chemicals such as acids like phosphoric acid or bases like
potassium hydroxide, sodium hydroxide or salts like zinc chloride,
followed by carbonization. "Activated" refers to a material or
substance, for example a carbon material, which has undergone the
process of activation.
[0073] "Carbonizing", "pyrolyzing", "carbonization" and "pyrolysis"
each refer to the process of heating a carbon-containing substance
at a pyrolysis dwell temperature in an inert atmosphere (e.g.,
argon, nitrogen or combinations thereof) or in a vacuum such that
the targeted material collected at the end of the process is
primarily carbon. "Pyrolyzed" refers to a material or substance,
for example a carbon material, which has undergone the process of
pyrolysis.
[0074] "Dwell temperature" refers to the temperature of the furnace
during the portion of a process which is reserved for maintaining a
relatively constant temperature (i.e., neither increasing nor
decreasing the temperature). For example, the pyrolysis dwell
temperature refers to the relatively constant temperature of the
furnace during pyrolysis, and the activation dwell temperature
refers to the relatively constant temperature of the furnace during
activation.
[0075] "Pore" refers to an opening or depression in the surface, or
a tunnel in a carbon material, such as for example activated
carbon, pyrolyzed dried polymer gels, pyrolyzed polymer cryogels,
pyrolyzed polymer xerogels, pyrolyzed polymer aerogels, activated
dried polymer gels, activated polymer cryogels, activated polymer
xerogels, activated polymer aerogels and the like. A pore can be a
single tunnel or connected to other tunnels in a continuous network
throughout the structure.
[0076] "Pore structure" refers to the layout of the surface of the
internal pores within a carbon material, such as an activated
carbon material. Components of the pore structure include pore
size, pore volume, surface area, density, pore size distribution
and pore length. Generally the pore structure of activated carbon
material comprises micropores and mesopores.
[0077] "Mesopore" generally refers to pores having a diameter
between about 2 nanometers and about 50 nanometers while the term
"micropore" refers to pores having a diameter less than about 2
nanometers. Mesoporous carbon materials comprise greater than 50%
of their total pore volume in mesopores while microporous carbon
materials comprise greater than 50% of their total pore volume in
micropores.
[0078] "Surface area" refers to the total specific surface area of
a substance measurable by the BET technique. Surface area is
typically expressed in units of m.sup.2/g. The BET
(Brunauer/Emmett/Teller) technique employs an inert gas, for
example nitrogen, to measure the amount of gas adsorbed on a
material and is commonly used in the art to determine the
accessible surface area of materials.
[0079] "Connected" when used in reference to mesopores and
micropores refers to the spatial orientation of such pores.
[0080] "Effective length" refers to the portion of the length of
the pore that is of sufficient diameter such that it is available
to accept salt ions from the electrolyte.
[0081] "Electrode" refers to a conductor through which electricity
enters or leaves an object, substance or region.
[0082] "Binder" refers to a material capable of holding individual
particles of a substance (e.g., a carbon material) together such
that after mixing a binder and the particles together the resulting
mixture can be formed into sheets, pellets, disks or other shapes.
Non-exclusive examples of binders include fluoro polymers, such as,
for example, PTFE (polytetrafluoroethylene, Teflon), PFA
(perfluoroalkoxy polymer resin, also known as Teflon), FEP
(fluorinated ethylene propylene, also known as Teflon), ETFE
(polyethylenetetrafluoroethylene, sold as Tefzel and Fluon), PVF
(polyvinyl fluoride, sold as Tedlar), ECTFE
(polyethylenechlorotrifluoroethylene, sold as Halar), PVDF
(polyvinylidene fluoride, sold as Kynar), PCTFE
(polychlorotrifluoroethylene, sold as Kel-F and CTFE),
trifluoroethanol and combinations thereof.
[0083] "Expander" refers to an additive used for adjusting the
electrochemical and physical properties of a carbon-lead blend.
Expanders may be included in electrodes comprising carbon-lead
blends. Suitable expanders are known in the art and are available
from commercial sources such as Hammond Expanders, USA.
[0084] "Inert" refers to a material that is not active in the
electrolyte of an electrical energy storage device, that is it does
not absorb a significant amount of ions or change chemically, e.g.,
degrade.
[0085] "Conductive" refers to the ability of a material to conduct
electrons through transmission of loosely held valence
electrons.
[0086] "Current collector" refers to a part of an electrical energy
storage and/or distribution device which provides an electrical
connection to facilitate the flow of electricity in to, or out of,
the device. Current collectors often comprise metal and/or other
conductive materials and may be used as a backing for electrodes to
facilitate the flow of electricity to and from the electrode.
[0087] "Electrolyte" means a substance containing free ions such
that the substance is electrically conductive. Electrolytes are
commonly employed in electrical energy storage devices. Examples of
electrolytes include, but are not limited to, sulfuric acid.
[0088] "Elemental form" refers to a chemical element having an
oxidation state of zero (e.g., metallic lead).
[0089] "Oxidized form" form refers to a chemical element having an
oxidation state greater than zero.
[0090] "Total Pore Volume" refers to single point nitrogen
sorption
[0091] "DFT Pore Volume" refers to pore volume within certain pore
size ranges calculated by density functional theory from nitrogen
sorption data.
A. Blends of Carbon Particles and Lead Particles
[0092] The present disclosure is directed to blends comprising a
plurality of carbon particles (i.e., particles comprising carbon)
and a plurality of lead particles (i.e., particles comprising
lead). In certain embodiments, the blends result from physically
mixing a plurality of carbon particles and a plurality of lead
particles and thus have different properties than carbon materials
comprising lead within the carbon pores or on the carbon surface,
etc. Thus, in some embodiments the blends comprise distinct carbon
particles and distinct lead particles. The properties of the blends
are particularly suited to the disclosed hybrid energy storage
devices, and the properties can be optimized by varying any one of
several parameters as discussed below. For example, the purity of
the carbon particles (e.g., ultrapure or non-ultrapure), pore size
distribution of the carbon particles and relative amount of carbon
particles in the blend are just a few parameters that can be varied
and optimized to obtain the desired electrochemical properties.
[0093] The disclosed blend comprises a plurality of carbon
particles and a plurality of lead particles. The mass percent of
carbon particles as a percentage of the total mass of carbon
particles and lead particles can be varied from 0.01% to 99.9%. In
other various embodiments the mass percent of carbon particles as a
percentage of the total mass of carbon particles and lead particles
ranges from 0.01% to 20%, for example from 0.1% to 10% or from 1.0%
to 2.0%. In other embodiments, the mass percent of carbon particles
as a percentage of the total mass of carbon particles and lead
particles ranges from 0.01% to 2%, from 0.5% to 2.5% or from 0.75%
to 2.25%. In some other embodiments, the mass percent of carbon
particles as a percentage of the total mass of carbon particles and
lead particles ranges from 0.9% to 1.1%, from 1.1% to 1.3%, from
1.3% to 1.5%, from 1.5% to 1.7%, from 1.7% to 1.9% or from 1.9% to
2.1%. In some embodiments the mass percent of carbon particles as a
percentage of the total mass of carbon particles and lead particles
is about 50%.
[0094] Alternatively, in other embodiments the mass percent of
carbon particles as a percentage of the total mass of carbon
particles and lead particles ranges from 0.1% to 50%, from 0.1% to
10%, from 1% to 10%, from 1% to 5% or 1% to 3%. In still other
embodiments, the mass percent of carbon particles as a percentage
of the total mass of carbon particles and lead particles ranges
from 50% to 99.9%, from 90% to 99.9% or from 90% to 99%.
[0095] The volume percent of carbon particles as a percentage of
the total volume of carbon particles and lead particles can be
varied from 0.1% to 99.9%. In various embodiments the volume
percent of carbon particles as a percentage of the total volume of
carbon particles and lead particles ranges from 1% to 99%, from 2%
to 99%, from 3% to 99%, from 4% to 99%, from 5% to 99%, from 6% to
99%, from 7% to 99%, from 8% to 99%, from 9% to 99%, from 10% to
90%, from 20% to 80%, from 20% to 40%, from 1% to 20%, from 40% to
80% or from 40% to 60%. In some certain embodiment the volume
percent of carbon particles as a percentage of the total volume of
carbon particles and lead particles is about 50%.
[0096] In other alternative embodiments, the volume percent of
carbon particles as a percentage of the total volume of carbon
particles and lead particles ranges from 0.1% to 50%, from 0.1% to
10% or from 1% to 10%. In other embodiments, the volume percent of
carbon particles as a percentage of the total volume of carbon
particles and lead particles ranges from 50% to 99.9%, from 90% to
99.9% or from 90% to 99%.
[0097] The surface area percent of carbon particles as a percentage
of the total surface area of carbon particles and lead particles
can also be varied, for example from 0.1% to 99.9%. In some
embodiments the surface area percent of carbon particles as a
percentage of the total surface area of carbon particles and lead
particles ranges from 1% to 99%, from 10% to 90%, from 20% to 80%
or from 40% to 60%. In another embodiment, the surface area percent
of carbon particles as a percentage of the total surface area of
carbon particles and lead particles is about 50%.
[0098] In related embodiments, the surface area percent of carbon
particles as a percentage of the total surface area of carbon
particles and lead particles ranges from 0.1% to 50%, from 0.1% to
10% or from 1% to 10%. In other embodiments, the surface area
percent of carbon particles as a percentage of the total surface
area of carbon particles and lead particles ranges from 80% to
100%, for example from 80% to 99.9%, from 80% to 99%, from 85% to
99% or from 90% to 99%, For example, in some embodiments the
surface area percent of carbon particles as a percentage of the
total surface area of carbon particles and lead particles ranges
from 90% to 92%, from 92%, from 92% to 94%, from 94% to 96%, from
96% to 98% or from 93% to 99% or even to 99.9%. Alternatively, the
surface area percent of carbon particles as a percentage of the
total surface area of carbon particles and lead particles ranges
from 50% to 99.9%, from 90% to 99.9% or from 90% to 99%.
[0099] The carbon particle surface area residing in pores less than
20 angstroms as a percentage of the total surface area residing in
pores less than 20 angstroms of carbon particles and lead particles
can be varied from 0.1% to 99.9%. In some embodiments, the carbon
particle surface area residing in pores less than 20 angstroms as a
percentage of the total surface area residing in pores less than 20
angstroms of carbon particles and lead particles ranges from 1% to
99%, from 10% to 90%, from 20% to 80%, from 20% to 60% or from 40%
to 60%. In another embodiment, the carbon particle surface area
residing in pores less than 20 angstroms as a percentage of the
total surface area residing in pores less than 20 angstroms of
carbon particles and lead particles is about 50%.
[0100] In other related embodiments, the carbon particle surface
area residing in pores less than 20 angstroms as a percentage of
the total surface area residing in pores less than 20 angstroms of
carbon particles and lead particles ranges from 0.1% to 50%, 0.1%
to 10% or from 1% to 10%. Alternatively, the carbon particle
surface area residing in pores less than 20 angstroms as a
percentage of the total surface area residing in pores less than 20
angstroms of carbon particles and lead particles ranges from 50% to
99.9%, from 90% to 99.9% or from 90% to 99%.
[0101] In another embodiment, the carbon particle surface area
residing in pores greater than 20 angstroms as a percentage of the
total surface area residing in pores greater than 20 angstroms of
carbon particles and lead particles ranges from 0.1% to 99.9%. For
example, in various embodiments, the carbon particle surface area
residing in pores greater than 20 angstroms as a percentage of the
total surface area residing in pores greater than 20 angstroms of
carbon particles and lead particles ranges from 1% to 99%, from 10%
to 90%, from 20% to 80% or from 40% to 6%. In a certain embodiment,
the carbon particle surface area residing in pores greater than 20
angstroms as a percentage of the total surface area residing in
pores greater than 20 angstroms of carbon particles and lead
particles ranges from is about 50%.
[0102] Alternatively, in a different embodiment, the carbon
particle surface area residing in pores greater than 20 angstroms
as a percentage of the total surface area residing in pores greater
than 20 angstroms of carbon particles and lead particles ranges
from 0.1% to 50%. For example, in some embodiments, the carbon
particle surface area residing in pores greater than 20 angstroms
as a percentage of the total surface area residing in pores greater
than 20 angstroms of carbon particles and lead particles ranges
from 0.1% to 10% or from 1% to 10%. In another embodiment, the
carbon particle surface area residing in pores greater than 20
angstroms as a percentage of the total surface area residing in
pores greater than 20 angstroms of carbon particles and lead
particles ranges from 50% to 99.9%, from 90% to 99.9% or from 90%
to 99%.
[0103] In some embodiments, the volume average particle size of the
carbon particles relative to the volume average particle size of
the lead particles ranges from 0.000001:1 to 100000:1. For example,
in some embodiments the volume average particle size of carbon
particles relative to the volume average particle size of lead
particles ranges from 0.0001:1 to 10000:1, from 0.001:1 to 1000:1,
from 0.01:1 to 100:1, from 0.01:1 to 10:1, from 0.1:1 to 2:1, from
0.1:1 to 10:1 or from 1:1 to 1000:1. In one embodiment the volume
average particle size of the carbon particles relative to the
volume average particle size of the lead particles is about
1:1.
[0104] In certain embodiments, the composition of particles is
comprised of more than one population of carbon particles and/or
more than one population of lead particles. The different
populations can be different with respect to various
physical-chemical attributes such as, particle size, extent of
meso- or micro-porosity, surface functionality, and the like. For
example, in some embodiments, the blend comprises a multi-modal
carbon particle size distribution and lead particles. For example,
the carbon particles can be comprised of two size modes. For
example, in some embodiments the ratio between the two size modes
ranges from 0.000001:1 to 100000:1, for example in a one embodiment
the ratio between the two size modes is about 0.001:1.
[0105] The lead particles can be any type of particle which
comprises lead. For example, the lead particles may comprise
elemental lead, oxidized lead and/or lead salts. In certain
embodiments, the lead particles comprise lead (II) oxide, lead (IV)
oxide, lead acetate, lead carbonate, lead sulfate, lead
orthoarsenate, lead pyroarsenate, lead bromide, lead caprate, lead
carproate, lead caprylate, lead chlorate, lead chloride, lead
fluoride, lead nitrate, lead oxychloride, lead orthophosphate
sulfate, lead chromate, lead chromate, basic, lead ferrite, lead
sulfide, lead tungstate or combinations thereof.
[0106] The capacitance of the carbon-lead blends varies depending
on the physiochemical properties of the carbon and lead particles.
In certain embodiments, the capacitance of the carbon-lead blends
is greater than 500 F/g of carbon particles in the blend, greater
than 450 F/g of carbon particles in the blend, greater than 400 F/g
of carbon particles in the blend, greater than 350 F/g of carbon
particles in the blend, greater than 300 F/g of carbon particles in
the blend, greater than 250 F/g of carbon particles in the blend,
greater than 200 F/g of carbon particles in the blend or even
greater than 150 F/g of carbon particles in the blend. In certain
embodiments of the foregoing, the capacitance is measured in a
sulfuric acid electrolyte. For example, in some embodiments the
capacitance is measured based on the discharge data of a
galvanostatic charge/discharge profile to 0.9V and 0V at a
symmetric current density ranging from 0.1 A/g carbon to 10 A/g
carbon, for example 1 A/g (see e.g., Example 28).
[0107] In still other embodiments, the capacitance of the
carbon-lead blends is measured based on surface area of the blend.
Accordingly, in certain embodiments the carbon-lead blends comprise
a capacitance of greater than 2.0 F/m.sup.2, greater than 1.75
F/m.sup.2, greater than 1.50 F/m.sup.2, greater than 1.25
F/m.sup.2, greater than 1.0 F/m.sup.2, greater than 0.75 F/m.sup.2,
greater than 0.5 F/m.sup.2, greater than 0.25 F/m.sup.2, greater
than 0.1 F/m.sup.2 or even greater than 0.01 F/m.sup.2. In certain
embodiments of the foregoing, the capacitance is measured in a
sulfuric acid electrolyte. For example, the in some embodiments the
capacitance is measured based on the discharge data of a
galvanostatic charge/discharge profile to 0.9V and 0V at a
symmetric current density ranging from 0.1 A/g carbon to 10 A/g
carbon (see e.g., Example 28). One skilled in the art will
understand how to determine the F/m.sup.2 of a carbon-lead blend,
for example the F/m.sup.2 value can be calculated by experimentally
determining the F/g and the using the density of the carbon-lead
composition (e.g., paste) to convert this value to F/m.sup.2.
[0108] The blends described herein may also be provided in the form
of a composition comprising the blend and a solvent (e.g.,
electrolyte), a binder, and expander or combinations thereof. In
certain embodiments the compositions are in the form of a paste.
The compositions can be prepared by admixing the carbon particles,
lead particles and the solvent (e.g., electrolyte), binder,
expander or combinations thereof. The density of the compositions
varies from about 2.0 g/cc to about 8 g/cc, from about 3.0 g/cc to
about 7.0 g/cc or from about 4.0 g/cc to about 6.0 g/cc. In still
other embodiments, the density of the composition is from about 3.5
g/cc to about 4.0 g/cc, from about 4.0 g/cc to about 4.5 g/cc, from
about 4.5 g/cc to about 5.0 g/cc, from about 5.0 g/cc to about 5.5
g/cc, from about 5.5 g/cc to about 6.0 g/cc, from about 6.0 g/cc to
about 6.5 g/cc, or from about 6.5 g/cc to about 7.0 g/cc.
[0109] The purity of the carbon-lead blends can contribute to the
electrochemical performance of the same. In this regard, the purity
is determined by PIXE analysis and PIXE impurity with respect to
the blend exclude any lead content. In some embodiments, the blend
comprises a total PIXE impurity content of elements (excluding any
lead) of less than 500 ppm and an ash content (excluding any lead)
of less than 0.08%. In further embodiments, the blend comprises a
total PIXE impurity content of all other elements of less than 300
ppm and an ash content of less than 0.05%. In other further
embodiments, the blend comprises a total PIXE impurity content of
all other elements of less than 200 ppm and an ash content of less
than 0.05%. In other further embodiments, the blend comprises a
total PIXE impurity content of all other elements of less than 200
ppm and an ash content of less than 0.025%. In other further
embodiments, the blend comprises a total PIXE impurity content of
all other elements of less than 100 ppm and an ash content of less
than 0.02%. In other further embodiments, the blend comprises a
total PIXE impurity content of all other elements of less than 50
ppm and an ash content of less than 0.01%.
[0110] The amount of individual PIXE impurities present in the
disclosed blends can be determined by proton induced x-ray
emission. Individual PIXE impurities may contribute in different
ways to the overall electrochemical performance of the disclosed
carbon materials. Thus, in some embodiments, the level of sodium
present in the blend is less than 1000 ppm, less than 500 ppm, less
than 100 ppm, less than 50 ppm, less than 10 ppm, or less than 1
ppm. In some embodiments, the level of magnesium present in the
blend is less than 1000 ppm, less than 100 ppm, less than 50 ppm,
less than 10 ppm, or less than 1 ppm. In some embodiments, the
level of aluminum present in the blend is less than 1000 ppm, less
than 100 ppm, less than 50 ppm, less than 10 ppm, or less than 1
ppm. In some embodiments, the level of silicon present in the blend
is less than 500 ppm, less than 300 ppm, less than 100 ppm, less
than 50 ppm, less than 20 ppm, less than 10 ppm or less than 1 ppm.
In some embodiments, the level of phosphorous present in the blend
is less than 1000 ppm, less than 100 ppm, less than 50 ppm, less
than 10 ppm, or less than 1 ppm. In some embodiments, the level of
sulfur present in the blend is less than 1000 ppm, less than 100
ppm, less than 50 ppm, less than 30 ppm, less than 10 ppm, less
than 5 ppm or less than 1 ppm. In some embodiments, the level of
chlorine present in the blend is less than 1000 ppm, less than 100
ppm, less than 50 ppm, less than 10 ppm, or less than 1 ppm. In
some embodiments, the level of potassium present in the blend is
less than 1000 ppm, less than 100 ppm, less than 50 ppm, less than
10 ppm, or less than 1 ppm. In other embodiments, the level of
calcium present in the blend is less than 100 ppm, less than 50
ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm or less
than 1 ppm. In some embodiments, the level of chromium present in
the blend is less than 1000 ppm, less than 100 ppm, less than 50
ppm, less than 10 ppm, less than 5 ppm, less than 4 ppm, less than
3 ppm, less than 2 ppm or less than 1 ppm. In other embodiments,
the level of iron present in the blend is less than 50 ppm, less
than 20 ppm, less than 10 ppm, less than 5 ppm, less than 4 ppm,
less than 3 ppm, less than 2 ppm or less than 1 ppm. In other
embodiments, the level of nickel present in the blend is less than
20 ppm, less than 10 ppm, less than 5 ppm, less than 4 ppm, less
than 3 ppm, less than 2 ppm or less than 1 ppm. In some other
embodiments, the level of copper present in the blend is less than
140 ppm, less than 100 ppm, less than 40 ppm, less than 20 ppm,
less than 10 ppm, less than 5 ppm, less than 4 ppm, less than 3
ppm, less than 2 ppm or less than 1 ppm. In yet other embodiments,
the level of zinc present in the blend is less than 20 ppm, less
than 10 ppm, less than 5 ppm, less than 2 ppm or less than 1 ppm.
In yet other embodiments, the sum of all other PIXE impurities
(excluding the lead) present in the blend is less than 1000 ppm,
less than 500 pm, less than 300 ppm, less than 200 ppm, less than
100 ppm, less than 50 ppm, less than 25 ppm, less than 10 ppm or
less than 1 ppm. As noted above, in some embodiments other
impurities such as hydrogen, oxygen and/or nitrogen may be present
in levels ranging from less than 10% to less than 0.01%.
[0111] In some embodiments, the blend comprise undesired PIXE
impurities near or below the detection limit of the proton induced
x-ray emission analysis. For example, in some embodiments the blend
comprises less than 50 ppm sodium, less than 15 ppm magnesium, less
than 10 ppm aluminum, less than 8 ppm silicon, less than 4 ppm
phosphorous, less than 3 ppm sulfur, less than 3 ppm chlorine, less
than 2 ppm potassium, less than 3 ppm calcium, less than 2 ppm
scandium, less than 1 ppm titanium, less than 1 ppm vanadium, less
than 0.5 ppm chromium, less than 0.5 ppm manganese, less than 0.5
ppm iron, less than 0.25 ppm cobalt, less than 0.25 ppm nickel,
less than 0.25 ppm copper, less than 0.5 ppm zinc, less than 0.5
ppm gallium, less than 0.5 ppm germanium, less than 0.5 ppm
arsenic, less than 0.5 ppm selenium, less than 1 ppm bromine, less
than 1 ppm rubidium, less than 1.5 ppm strontium, less than 2 ppm
yttrium, less than 3 ppm zirconium, less than 2 ppm niobium, less
than 4 ppm molybdenum, less than 4 ppm, technetium, less than 7 ppm
rubidium, less than 6 ppm rhodium, less than 6 ppm palladium, less
than 9 ppm silver, less than 6 ppm cadmium, less than 6 ppm indium,
less than 5 ppm tin, less than 6 ppm antimony, less than 6 ppm
tellurium, less than 5 ppm iodine, less than 4 ppm cesium, less
than 4 ppm barium, less than 3 ppm lanthanum, less than 3 ppm
cerium, less than 2 ppm praseodymium, less than 2 ppm, neodymium,
less than 1.5 ppm promethium, less than 1 ppm samarium, less than 1
ppm europium, less than 1 ppm gadolinium, less than 1 ppm terbium,
less than 1 ppm dysprosium, less than 1 ppm holmium, less than 1
ppm erbium, less than 1 ppm thulium, less than 1 ppm ytterbium,
less than 1 ppm lutetium, less than 1 ppm hafnium, less than 1 ppm
tantalum, less than 1 ppm tungsten, less than 1.5 ppm rhenium, less
than 1 ppm osmium, less than 1 ppm iridium, less than 1 ppm
platinum, less than 1 ppm silver, less than 1 ppm mercury, less
than 1 ppm thallium, less than 1.5 ppm bismuth, less than 2 ppm
thorium, or less than 4 ppm uranium.
[0112] In some specific embodiments, the blend comprises less than
100 ppm sodium, less than 300 ppm silicon, less than 50 ppm sulfur,
less than 100 ppm calcium, less than 20 ppm iron, less than 10 ppm
nickel, less than 140 ppm copper, less than 5 ppm chromium and less
than 5 ppm zinc as measured by proton induced x-ray emission. In
other specific embodiments, the blend comprises less than 50 ppm
sodium, less than 30 ppm sulfur, less than 100 ppm silicon, less
than 50 ppm calcium, less than 10 ppm iron, less than 5 ppm nickel,
less than 20 ppm copper, less than 2 ppm chromium and less than 2
ppm zinc.
[0113] In other specific embodiments, the blend comprises less than
50 ppm sodium, less than 50 ppm silicon, less than 30 ppm sulfur,
less than 10 ppm calcium, less than 2 ppm iron, less than 1 ppm
nickel, less than 1 ppm copper, less than 1 ppm chromium and less
than 1 ppm zinc.
[0114] In some other specific embodiments, the blend comprises less
than 100 ppm sodium, less than 50 ppm magnesium, less than 50 ppm
aluminum, less than 10 ppm sulfur, less than 10 ppm chlorine, less
than 10 ppm potassium, less than 1 ppm chromium and less than 1 ppm
manganese.
[0115] In other embodiments, the blend comprises less than 5 ppm
chromium, less than 10 ppm iron, less than 5 ppm nickel, less than
20 ppm silicon, less than 5 ppm zinc, and bismuth, silver, copper,
mercury, manganese, platinum, antimony and tin are not detected as
measured by proton induced x-ray emission.
[0116] In other embodiments, the blend comprises less than 75 ppm
bismuth, less than 5 ppm silver, less than 10 ppm chromium, less
than 30 ppm copper, less than 30 ppm iron, less than 5 ppm mercury,
less than 5 ppm manganese, less than 20 ppm nickel, less than 5 ppm
platinum, less than 10 ppm antimony, less than 100 ppm silicon,
less than 10 ppm tin and less than 10 ppm zinc as measured by
proton induced x-ray emission.
[0117] In other embodiments, the blend comprises less than 5 ppm
chromium, 10 ppm iron, less than 5 ppm nickel, less than 20 ppm
silicon, less than 5 ppm zinc and bismuth, silver, copper, mercury,
manganese, platinum, antimony and tin are not detected as measured
by proton induced x-ray emission as measured by proton induced
x-ray emission.
[0118] Other embodiments of the present invention include use of
the disclosed carbon-lead blends in an electrical energy storage
device. In some embodiments, the electrical energy storage device
is a battery. In other embodiments, the electrical energy storage
device is in a microhybrid, start-stop hybrid, mild-hybrid vehicle,
vehicle with electric turbocharging, vehicle with regenerative
braking, hybrid vehicle, an electric vehicle, industrial motive
power such as forklifts, electric bikes, golf carts, aerospace
applications, a power storage and distribution grid, a solar or
wind power system, a power backup system such as emergency backup
for portable military backup, hospitals or military infrastructure,
and manufacturing backup or a cellular tower power system.
Electrical energy storage devices are described in more detail
below.
B. Carbon Particles
[0119] Various properties of the carbon particles within the blends
can be varied to obtain the desired electrochemical result. As
discussed above, electrodes comprising carbon materials comprising
metals and/or metal compounds and having residual levels of various
impurities (e.g., sodium, chlorine, nickel, iron, etc.) are known
to have decreased cycle life, durability and performance.
Accordingly, one embodiment provides blends comprising a plurality
of carbon particles which are significantly more pure than other
known carbon materials and are thus expected to improve the
operation of any number of electrical energy storage and/or
distribution devices.
[0120] The high purity of the disclosed carbon particles in certain
embodiments can be attributed to the disclosed sol gel processes.
Applicants have discovered that when one or more polymer
precursors, for example a phenolic compound and an aldehyde, are
co-polymerized under acidic conditions in the presence of a
volatile basic catalyst, an ultrapure polymer gel results. This is
in contrast to other reported methods for the preparation of
polymer gels which result in polymer gels comprising residual
levels of undesired impurities. The ultrapure polymer gels can be
pyrolyzed by heating in an inert atmosphere (e.g., nitrogen) to
yield the carbon particles comprising a high surface area and high
pore volume. These carbon materials can be further activated
without the use of chemical activation techniques--which introduce
impurities--to obtain ultrapure activated carbon materials. The
carbon particles are prepared from activated carbon materials or,
in some instances, pyrolyzed but not activated carbon
materials.
[0121] In certain embodiments, the carbon particles comprise lead
within the pores or on the surface of the carbon particles. Thus
the blends may comprise a plurality of carbon particles, which
comprise lead, and a plurality of lead particles. Lead can be
incorporated into the carbon materials at various stages of the sol
gel process. For example, leads and/or lead compounds can be
incorporated during the polymerization stage, into the polymer gel
or into the pyrolyzed or activated carbon particles. The unique
porosity and high surface area of the carbon particles provides for
optimum contact of the electrode active material with the
electrolyte in, for example, a lead/acid battery. Electrodes
prepared from the disclosed blends comprise improved active life
and power performance relative to electrodes prepared from known
carbon materials.
[0122] In some embodiments, the carbon particles are a pyrolyzed
dried polymer gel, for example, a pyrolyzed polymer cryogel, a
pyrolyzed polymer xerogel or a pyrolyzed polymer aerogel. In other
embodiments, the carbon particles are activated (i.e., a synthetic
activated carbon material). For example, in further embodiments the
carbon particles are an activated dried polymer gel, an activated
polymer cryogel, an activated polymer xerogel or an activated
polymer aerogel.
[0123] The carbon particles can be of any source or purity. For
example, in some embodiments, the carbon particles can be ultrapure
activated carbon, wherein the carbon particles comprises less than
1000 PPM, for example less than 500 PPM for example less than 200
ppm, for example less than 100 ppm, for example less than 50 ppm,
or even less than 10 PPM of PIXE impurities. In other examples, the
carbon has levels of PXIE impurities ranging from 0.1 to 1000 ppm.
In other embodiments, the carbon particles have PIXE impurities
levels ranging from 900 to 1000 ppm. In other embodiments, the
carbon particles have PIXE impurities levels ranging from 800 to
900 ppm. In other embodiments, the carbon particles have PIXE
impurities levels ranging from 700 to 800 ppm. In other
embodiments, the carbon particles have PIXE impurities levels
ranging from 600 to 700 ppm. In other embodiments, the carbon
particles have PIXE impurities levels ranging from 500 to 600 ppm.
In other embodiments, the carbon particles have PIXE impurities
levels ranging from 400 to 500 ppm. In other embodiments, the
carbon particles have PIXE impurities levels ranging from 300 to
400 ppm. In other embodiments, the carbon particles have PIXE
impurities levels ranging from 200 to 300 ppm. In other
embodiments, the carbon particles have PIXE impurities levels
ranging from 100 to 200 ppm. In other embodiments, the carbon
particles have PIXE impurities levels ranging from 0.1 to 100 ppm.
In other embodiments, the carbon particles have PIXE impurities
levels ranging from 0.1 to 50 ppm. In other embodiments, the carbon
particles have PIXE impurities levels ranging from 0.1 to 10
ppm.
[0124] The carbon particles may also be "non-ultrapure" (i.e.,
greater than 100 PPM of PIXE impurities. For example, in some
embodiments, the level of total impurities in the non-ultrapure
activated carbon (as measured by proton induced x-ray emission) is
in the range of about 1000 ppm or greater, for example 2000 ppm.
The ash content of the non-ultrapure carbon is in the range of
about 0.1% or greater, for example 0.41%. In addition, the
non-ultrapure carbon materials can be incorporated into devices
suitable for energy storage and distribution, for example in
ultracapacitors.
[0125] The carbon particles may also comprise lead in addition to
being physically blended with lead particles. This results in a
blend of lead containing carbon particles and lead particles. Such
blends find particular utility in the hybrid devices described
herein. In this regard, the carbon particles may be of any purity
level, and the lead may be incorporated into the pores of the
carbon particles and/or on the surface of the carbon particles.
Accordingly, in some embodiments the carbon composition comprises a
plurality of carbon particles and a plurality of lead particles,
wherein the carbon particles comprise lead, for example at least
1000 PPM of lead. In certain other embodiments of the foregoing,
the carbon particles comprise lead and less than 500 PPM of all
other PIXE impurities. In some other embodiments, the carbon
particles comprise at least 0.10%, at least 0.25%, at least 0.50%,
at least 1.0%, at least 5.0%, at least 10%, at least 25%, at least
50%, at least 75%, at least 90%, at least 95%, at least 99% or at
least 99.5% of lead. For example, in some embodiments, the carbon
particles comprise between 0.5% and 99.5% activated carbon and
between 0.5% and 99.5% lead. The percent of lead is calculated on
weight percent basis (wt %).
[0126] The lead in any of the embodiments disclosed herein can be
in any number of forms. For example, in some embodiments, the lead
is in the form of elemental lead, lead (II) oxide, lead (IV) oxide
or combinations thereof. In other embodiments, the lead is in the
form of lead acetate, lead carbonate, lead sulfate, lead
orthoarsenate, lead pyroarsenate, lead bromide, lead caprate, lead
carproate, lead caprylate, lead chlorate, lead chloride, lead
fluoride, lead nitrate, lead oxychloride, lead orthophosphate
sulfate, lead chromate, lead chromate, basic, lead ferrite, lead
sulfide, lead tungstate or combinations thereof. Other lead salts
are also contemplated.
[0127] In some embodiments, the carbon particles comprise at least
1,000 ppm of lead. In other embodiments, the carbon material
comprises a total of less than 500 ppm of elements (excluding any
intentionally added lead) having atomic numbers ranging from 11 to
92, for example, less than 200 ppm, less than 100 ppm, less than 50
ppm, less than 25 ppm, less than 10 ppm, less than 5 ppm or less
than 1 ppm. In certain embodiments the lead content and/or the PIXE
impurity content is measured by proton induced x-ray emission
analysis.
[0128] Certain metal elements such as iron, cobalt, nickel,
chromium, copper, titanium, vanadium and rhenium may decrease the
electrical performance of electrodes comprising the blends.
Accordingly, in some embodiments, the carbon particles comprise low
levels of one or more of these elements. For example, in certain
embodiments, the carbon particles comprise less than 100 ppm iron,
less than 50 ppm iron, less than 25 ppm iron, less than 10 ppm
iron, less than 5 ppm iron or less than 1 ppm iron. In other
embodiments, the carbon particles comprise less than 100 ppm
cobalt, less than 50 ppm cobalt, less than 25 ppm cobalt, less than
10 ppm cobalt, less than 5 ppm cobalt or less than 1 ppm cobalt. In
other embodiments, the carbon particles comprise less than 100 ppm
nickel, less than 50 ppm nickel, less than 25 ppm nickel, less than
10 ppm nickel, less than 5 ppm nickel or less than 1 ppm nickel. In
other embodiments, the carbon particles comprise less than 100 ppm
chromium, less than 50 ppm chromium, less than 25 ppm chromium,
less than 10 ppm chromium, less than 5 ppm chromium or less than 1
ppm chromium. In other embodiments, the carbon particles comprise
less than 100 ppm copper, less than 50 ppm copper, less than 25 ppm
copper, less than 10 ppm copper, less than 5 ppm copper or less
than 1 ppm copper. In other embodiments, the carbon particles
comprise less than 100 ppm titanium, less than 50 ppm titanium,
less than 25 ppm titanium, less than 10 ppm titanium, less than 5
ppm titanium or less than 1 ppm titanium. In other embodiments, the
carbon particles comprise less than 100 ppm vanadium, less than 50
ppm vanadium, less than 25 ppm vanadium, less than 10 ppm vanadium,
less than 5 ppm vanadium or less than 1 ppm vanadium. In other
embodiments, the carbon particles comprise less than 100 ppm
rhenium, less than 50 ppm rhenium, less than 25 ppm rhenium, less
than 10 ppm rhenium, less than 5 ppm rhenium or less than 1 ppm
rhenium.
[0129] In other embodiments, the carbon particles comprise less
than 5 ppm chromium, less than 10 ppm iron, less than 5 ppm nickel,
less than 20 ppm silicon, less than 5 ppm zinc, and bismuth,
silver, copper, mercury, manganese, platinum, antimony and tin are
not detected as measured by proton induced x-ray emission.
[0130] In other embodiments, the carbon particles comprise less
than 75 ppm bismuth, less than 5 ppm silver, less than 10 ppm
chromium, less than 30 ppm copper, less than 30 ppm iron, less than
5 ppm mercury, less than 5 ppm manganese, less than 20 ppm nickel,
less than 5 ppm platinum, less than 10 ppm antimony, less than 100
ppm silicon, less than 10 ppm tin and less than 10 ppm zinc as
measured by proton induced x-ray emission.
[0131] In other embodiments, the carbon particles comprise less
than 5 ppm chromium, 10 ppm iron, less than 5 ppm nickel, less than
20 ppm silicon, less than 5 ppm zinc and bismuth, silver, copper,
mercury, manganese, platinum, antimony and tin are not detected as
measured by proton induced x-ray emission as measured by proton
induced x-ray emission.
[0132] The porosity of the carbon particles is an important
parameter for electrochemical performance of the blends.
Accordingly, in one embodiment the carbon particles comprise a DFT
pore volume of at least 0.35 cc/g, at least 0.30 cc/g, at least
0.25 cc/g, at least 0.20 cc/g, at least 0.15 cc/g, at least 0.10
cc/g, at least 0.05 cc/g or at least 0.01 cc/g for pores less than
20 angstroms. In other embodiments the carbon particles are devoid
of any measurable pore volume. In other embodiments, the carbon
particles comprise a DFT pore volume of at least 4.00 cc/g, at
least 3.75 cc/g, at least 3.50 cc/g, at least 3.25 cc/g, at least
3.00 cc/g, at least 2.75 cc/g, at least 2.50 cc/g, at least 2.25
cc/g, at least 2.00 cc/g, at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g,
1.60 cc/g, 1.50 cc/g, 1.40 cc/g, at least 1.30 cc/g, at least 1.20
cc/g, at least 1.10 cc/g, at least 1.00 cc/g, at least 0.85 cc/g,
at least 0.80 cc/g, at least 0.75 cc/g, at least 0.70 cc/g or at
least 0.65 cc/g for pores greater than 20 angstroms.
[0133] In other embodiments, the carbon particles comprise a DFT
pore volume of at least 4.00 cc/g, at least 3.75 cc/g, at least
3.50 cc/g, at least 3.25 cc/g, at least 3.00 cc/g, at least 2.75
cc/g, at least 2.50 cc/g, at least 2.25 cc/g, at least 2.00 cc/g,
at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g, 1.60 cc/g, 1.50 cc/g,
1.40 cc/g, at least 1.30 cc/g, at least 1.20 cc/g, at least 1.10
cc/g, at least 1.00 cc/g, at least 0.85 cc/g, at least 0.80 cc/g,
at least 0.75 cc/g, at least 0.70 cc/g, at least 0.65 cc/g, at
least 0.60 cc/g, at least 0.55 cc/g, at least 0.50 cc/g, at least
0.45 cc/g, at least 0.40 cc/g, at least 0.35 cc/g, at least 0.30
cc/g, at least 0.25 cc/g, at least 0.20 cc/g, at least 0.15 cc/g,
or at least 0.10 cc/g for pores ranging from 20 angstroms to 500
angstroms.
[0134] In other embodiments, the carbon particles comprise a DFT
pore volume of at least 4.00 cc/g, at least 3.75 cc/g, at least
3.50 cc/g, at least 3.25 cc/g, at least 3.00 cc/g, at least 2.75
cc/g, at least 2.50 cc/g, at least 2.25 cc/g, at least 2.00 cc/g,
at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g, 1.60 cc/g, 1.50 cc/g,
1.40 cc/g, at least 1.30 cc/g, at least 1.20 cc/g, at least 1.10
cc/g, at least 1.00 cc/g, at least 0.85 cc/g, at least 0.80 cc/g,
at least 0.75 cc/g, at least 0.70 cc/g, at least 0.65 cc/g, at
least 0.60 cc/g, at least 0.55 cc/g, at least 0.50 cc/g, at least
0.45 cc/g, at least 0.40 cc/g, at least 0.35 cc/g, at least 0.30
cc/g, at least 0.25 cc/g, at least 0.20 cc/g, at least 0.15 cc/g,
or at least 0.10 cc/g for pores ranging from 20 angstroms to 1000
angstroms.
[0135] In other embodiments, the carbon particle comprises a DFT
pore volume of at least 4.00 cc/g, at least 3.75 cc/g, at least
3.50 cc/g, at least 3.25 cc/g, at least 3.00 cc/g, at least 2.75
cc/g, at least 2.50 cc/g, at least 2.25 cc/g, at least 2.00 cc/g,
at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g, 1.60 cc/g, 1.50 cc/g,
1.40 cc/g, at least 1.30 cc/g, at least 1.20 cc/g, at least 1.10
cc/g, at least 1.00 cc/g, at least 0.85 cc/g, at least 0.80 cc/g,
at least 0.75 cc/g, at least 0.70 cc/g, at least 0.65 cc/g, at
least 0.60 cc/g, at least 0.55 cc/g, at least 0.50 cc/g, at least
0.45 cc/g, at least 0.40 cc/g, at least 0.35 cc/g, at least 0.30
cc/g, at least 0.25 cc/g, at least 0.20 cc/g, at least 0.15 cc/g,
or at least 0.10 cc/g for pores ranging from 20 angstroms to 2000
angstroms.
[0136] In other embodiments, the carbon particles comprises a DFT
pore volume of at least 4.00 cc/g, at least 3.75 cc/g, at least
3.50 cc/g, at least 3.25 cc/g, at least 3.00 cc/g, at least 2.75
cc/g, at least 2.50 cc/g, at least 2.25 cc/g, at least 2.00 cc/g,
at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g, 1.60 cc/g, 1.50 cc/g,
1.40 cc/g, at least 1.30 cc/g, at least 1.20 cc/g, at least 1.10
cc/g, at least 1.00 cc/g, at least 0.85 cc/g, at least 0.80 cc/g,
at least 0.75 cc/g, at least 0.70 cc/g, at least 0.65 cc/g, at
least 0.60 cc/g, at least 0.55 cc/g, at least 0.50 cc/g, at least
0.45 cc/g, at least 0.40 cc/g, at least 0.35 cc/g, at least 0.30
cc/g, at least 0.25 cc/g, at least 0.20 cc/g, at least 0.15 cc/g,
or at least 0.10 cc/g for pores ranging from 20 angstroms to 5000
angstroms.
[0137] In yet other embodiments, the carbon particles comprise a
total DFT pore volume of at least 4.00 cc/g, at least 3.75 cc/g, at
least 3.50 cc/g, at least 3.25 cc/g, at least 3.00 cc/g, at least
2.75 cc/g, at least 2.50 cc/g, at least 2.25 cc/g, at least 2.00
cc/g, at least 1.90 cc/g, 1.80 cc/g, 1.70 cc/g, 1.60 cc/g, 1.50
cc/g, 1.40 cc/g, at least 1.30 cc/g, at least 1.20 cc/g, at least
1.10 cc/g, at least 1.00 cc/g, at least 0.85 cc/g, at least 0.80
cc/g, at least 0.75 cc/g, at least 0.70 cc/g, at least 0.65 cc/g,
at least 0.60 cc/g, at least 0.55 cc/g, at least 0.50 cc/g, at
least 0.45 cc/g, at least 0.40 cc/g, at least 0.35 cc/g, at least
0.30 cc/g, at least 0.25 cc/g, at least 0.20 cc/g, at least 0.15
cc/g, or at least 0.10 cc/g.
[0138] In certain embodiments mesoporous carbon particles having
very little microporosity (e.g., less than 30%, less than 20%, less
than 10% or less than 5% microporosity) are provided. The pore
volume and surface area of such carbon particles are advantageous
for inclusion of lead and electrolyte ions in certain embodiments.
For example, the mesoporous carbon can be a polymer gel that has
been pyrolyzed, but not activated. In some embodiments, the
mesoporous carbon comprises a specific surface area of at least 100
m.sup.2/g, at least 200 m.sup.2/g, at least 300 m.sup.2/g, at least
400 m.sup.2/g, at least 500 m.sup.2/g, at least 600 m.sup.2/g, at
least 675 m.sup.2/g or at least 750 m.sup.2/g. In other
embodiments, the mesoporous carbon particles comprise a total pore
volume of at least 0.50 cc/g, at least 0.60 cc/g, at least 0.70
cc/g, at least 0.80 cc/g, at least 0.90 cc/g, at least 1.0 cc/g or
at least 1.1 cc/g. In yet other embodiments, the mesoporous carbon
particles comprise a tap density of at least 0.30 g/cc, at least
0.35 g/cc, at least 0.40 g/cc, at least 0.45 g/cc, at least 0.50
g/cc or at least 0.55 g/cc.
[0139] In addition to low content of undesired PIXE impurities, the
disclosed carbon particles may comprise high total carbon content.
In addition to carbon, the carbon particles may also comprise
oxygen, hydrogen, nitrogen and the electrochemical modifier. In
some embodiments, the particles comprises at least 75% carbon, 80%
carbon, 85% carbon, at least 90% carbon, at least 95% carbon, at
least 96% carbon, at least 97% carbon, at least 98% carbon or at
least 99% carbon on a weight/weight basis. In some other
embodiments, the carbon particles comprises less than 10% oxygen,
less than 5% oxygen, less than 3.0% oxygen, less than 2.5% oxygen,
less than 1% oxygen or less than 0.5% oxygen on a weight/weight
basis. In other embodiments, the carbon particles comprises less
than 10% hydrogen, less than 5% hydrogen, less than 2.5% hydrogen,
less than 1% hydrogen, less than 0.5% hydrogen or less than 0.1%
hydrogen on a weight/weight basis. In other embodiments, the carbon
particles comprises less than 5% nitrogen, less than 2.5% nitrogen,
less than 1% nitrogen, less than 0.5% nitrogen, less than 0.25%
nitrogen or less than 0.01% nitrogen on a weight/weight basis. The
oxygen, hydrogen and nitrogen content of the disclosed carbon
particles can be determined by combustion analysis. Techniques for
determining elemental composition by combustion analysis are well
known in the art.
[0140] The total ash content of the carbon particles may, in some
instances, have an effect on the electrochemical performance of the
blends. Accordingly, in some embodiments, the ash content
(excluding any intentionally added lead) of the carbon particles
ranges from 0.1% to 0.001% weight percent ash, for example in some
specific embodiments the ash content of the carbon particles is
less than 0.1%, less than 0.08%, less than 0.05%, less than 0.03%,
than 0.025%, less than 0.01%, less than 0.0075%, less than 0.005%
or less than 0.001%.
[0141] In other embodiments, the carbon particles comprises a total
PIXE impurity content of elements (excluding any intentionally
added lead) of less than 500 ppm and an ash content (excluding any
intentionally added lead) of less than 0.08%. In further
embodiments, the carbon particles comprises a total PIXE impurity
content of all other elements of less than 300 ppm and an ash
content of less than 0.05%. In other further embodiments, the
carbon particles comprises a total PIXE impurity content of all
other elements of less than 200 ppm and an ash content of less than
0.05%. In other further embodiments, the carbon particles comprises
a total PIXE impurity content of all other elements of less than
200 ppm and an ash content of less than 0.025%. In other further
embodiments, the carbon particles comprises a total PIXE impurity
content of all other elements of less than 100 ppm and an ash
content of less than 0.02%. In other further embodiments, the
carbon particles comprises a total PIXE impurity content of all
other elements of less than 50 ppm and an ash content of less than
0.01%.
[0142] The amount of individual PIXE impurities present in the
disclosed carbon particles can be determined by proton induced
x-ray emission. Individual PIXE impurities may contribute in
different ways to the overall electrochemical performance of the
disclosed carbon materials. Thus, in some embodiments, the level of
sodium present in the carbon particles is less than 1000 ppm, less
than 500 ppm, less than 100 ppm, less than 50 ppm, less than 10
ppm, or less than 1 ppm. In some embodiments, the level of
magnesium present in the carbon particles is less than 1000 ppm,
less than 100 ppm, less than 50 ppm, less than 10 ppm, or less than
1 ppm. In some embodiments, the level of aluminum present in the
carbon particles is less than 1000 ppm, less than 100 ppm, less
than 50 ppm, less than 10 ppm, or less than 1 ppm. In some
embodiments, the level of silicon present in the carbon particles
is less than 500 ppm, less than 300 ppm, less than 100 ppm, less
than 50 ppm, less than 20 ppm, less than 10 ppm or less than 1 ppm.
In some embodiments, the level of phosphorous present in the carbon
particles is less than 1000 ppm, less than 100 ppm, less than 50
ppm, less than 10 ppm, or less than 1 ppm. In some embodiments, the
level of sulfur present in the carbon particles is less than 1000
ppm, less than 100 ppm, less than 50 ppm, less than 30 ppm, less
than 10 ppm, less than 5 ppm or less than 1 ppm. In some
embodiments, the level of chlorine present in the carbon particles
is less than 1000 ppm, less than 100 ppm, less than 50 ppm, less
than 10 ppm, or less than 1 ppm. In some embodiments, the level of
potassium present in the carbon particles is less than 1000 ppm,
less than 100 ppm, less than 50 ppm, less than 10 ppm, or less than
1 ppm. In other embodiments, the level of calcium present in the
carbon particles is less than 100 ppm, less than 50 ppm, less than
20 ppm, less than 10 ppm, less than 5 ppm or less than 1 ppm. In
some embodiments, the level of chromium present in the carbon
particles is less than 1000 ppm, less than 100 ppm, less than 50
ppm, less than 10 ppm, less than 5 ppm, less than 4 ppm, less than
3 ppm, less than 2 ppm or less than 1 ppm. In other embodiments,
the level of iron present in the carbon particles is less than 50
ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm, less than
4 ppm, less than 3 ppm, less than 2 ppm or less than 1 ppm. In
other embodiments, the level of nickel present in the carbon
particles is less than 20 ppm, less than 10 ppm, less than 5 ppm,
less than 4 ppm, less than 3 ppm, less than 2 ppm or less than 1
ppm. In some other embodiments, the level of copper present in the
carbon particles is less than 140 ppm, less than 100 ppm, less than
40 ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm, less
than 4 ppm, less than 3 ppm, less than 2 ppm or less than 1 ppm. In
yet other embodiments, the level of zinc present in the carbon
particles is less than 20 ppm, less than 10 ppm, less than 5 ppm,
less than 2 ppm or less than 1 ppm. In yet other embodiments, the
sum of all other PIXE impurities (excluding the electrochemical
modifier) present in the carbon particles is less than 1000 ppm,
less than 500 pm, less than 300 ppm, less than 200 ppm, less than
100 ppm, less than 50 ppm, less than 25 ppm, less than 10 ppm or
less than 1 ppm. As noted above, in some embodiments other
impurities such as hydrogen, oxygen and/or nitrogen may be present
in levels ranging from less than 10% to less than 0.01%.
[0143] In some embodiments, the carbon particles comprise undesired
PIXE impurities near or below the detection limit of the proton
induced x-ray emission analysis. For example, in some embodiments
the carbon particles comprises less than 50 ppm sodium, less than
15 ppm magnesium, less than 10 ppm aluminum, less than 8 ppm
silicon, less than 4 ppm phosphorous, less than 3 ppm sulfur, less
than 3 ppm chlorine, less than 2 ppm potassium, less than 3 ppm
calcium, less than 2 ppm scandium, less than 1 ppm titanium, less
than 1 ppm vanadium, less than 0.5 ppm chromium, less than 0.5 ppm
manganese, less than 0.5 ppm iron, less than 0.25 ppm cobalt, less
than 0.25 ppm nickel, less than 0.25 ppm copper, less than 0.5 ppm
zinc, less than 0.5 ppm gallium, less than 0.5 ppm germanium, less
than 0.5 ppm arsenic, less than 0.5 ppm selenium, less than 1 ppm
bromine, less than 1 ppm rubidium, less than 1.5 ppm strontium,
less than 2 ppm yttrium, less than 3 ppm zirconium, less than 2 ppm
niobium, less than 4 ppm molybdenum, less than 4 ppm, technetium,
less than 7 ppm rubidium, less than 6 ppm rhodium, less than 6 ppm
palladium, less than 9 ppm silver, less than 6 ppm cadmium, less
than 6 ppm indium, less than 5 ppm tin, less than 6 ppm antimony,
less than 6 ppm tellurium, less than 5 ppm iodine, less than 4 ppm
cesium, less than 4 ppm barium, less than 3 ppm lanthanum, less
than 3 ppm cerium, less than 2 ppm praseodymium, less than 2 ppm,
neodymium, less than 1.5 ppm promethium, less than 1 ppm samarium,
less than 1 ppm europium, less than 1 ppm gadolinium, less than 1
ppm terbium, less than 1 ppm dysprosium, less than 1 ppm holmium,
less than 1 ppm erbium, less than 1 ppm thulium, less than 1 ppm
ytterbium, less than 1 ppm lutetium, less than 1 ppm hafnium, less
than 1 ppm tantalum, less than 1 ppm tungsten, less than 1.5 ppm
rhenium, less than 1 ppm osmium, less than 1 ppm iridium, less than
1 ppm platinum, less than 1 ppm silver, less than 1 ppm mercury,
less than 1 ppm thallium, less than 1 ppm lead, less than 1.5 ppm
bismuth, less than 2 ppm thorium, or less than 4 ppm uranium.
[0144] In some specific embodiments, the carbon particles comprise
less than 100 ppm sodium, less than 300 ppm silicon, less than 50
ppm sulfur, less than 100 ppm calcium, less than 20 ppm iron, less
than 10 ppm nickel, less than 140 ppm copper, less than 5 ppm
chromium and less than 5 ppm zinc as measured by proton induced
x-ray emission. In other specific embodiments, the carbon particles
comprise less than 50 ppm sodium, less than 30 ppm sulfur, less
than 100 ppm silicon, less than 50 ppm calcium, less than 10 ppm
iron, less than 5 ppm nickel, less than 20 ppm copper, less than 2
ppm chromium and less than 2 ppm zinc.
[0145] In other specific embodiments, the carbon particles comprise
less than 50 ppm sodium, less than 50 ppm silicon, less than 30 ppm
sulfur, less than 10 ppm calcium, less than 2 ppm iron, less than 1
ppm nickel, less than 1 ppm copper, less than 1 ppm chromium and
less than 1 ppm zinc.
[0146] In some other specific embodiments, the carbon particles
comprise less than 100 ppm sodium, less than 50 ppm magnesium, less
than 50 ppm aluminum, less than 10 ppm sulfur, less than 10 ppm
chlorine, less than 10 ppm potassium, less than 1 ppm chromium and
less than 1 ppm manganese.
[0147] The disclosed carbon particles also comprise a high surface
area. While not wishing to be bound by theory, it is thought that
such high surface area may contribute, at least in part, to the
superior electrochemical performance of the blends. Accordingly, in
some embodiments, the carbon particles comprise a BET specific
surface area of at least 100 m.sup.2/g, at least 200 m.sup.2/g, at
least 300 m.sup.2/g, at least 400 m.sup.2/g, at least 500
m.sup.2/g, at least 600 m.sup.2/g, at least 700 m.sup.2/g, at least
800 m.sup.2/g, at least 900 m.sup.2/g, at least 1000 m.sup.2/g, at
least 1500 m.sup.2/g, at least 2000 m.sup.2/g, at least 2400
m.sup.2/g, at least 2500 m.sup.2/g, at least 2750 m.sup.2/g or at
least 3000 m.sup.2/g. For example, in some embodiments of the
foregoing, the carbon particles are activated.
[0148] In another embodiment, the carbon particles comprise a tap
density between 0.1 and 1.0 g/cc, between 0.2 and 0.8 g/cc, between
0.3 and 0.5 g/cc or between 0.4 and 0.5 g/cc. In another
embodiment, the carbon particles has a total pore volume of at
least 0.1 cm.sup.3/g, at least 0.2 cm.sup.3/g, at least 0.3
cm.sup.3/g, at least 0.4 cm3/g, at least 0.5 cm.sup.3/g, at least
0.7 cm.sup.3/g, at least 0.75 cm.sup.3/g, at least 0.9 cm.sup.3/g,
at least 1.0 cm.sup.3/g, at least 1.1 cm.sup.3/g, at least 1.2
cm.sup.3/g, at least 1.3 cm.sup.3/g, at least 1.4 cm.sup.3/g, at
least 1.5 cm.sup.3/g or at least 1.6 cm.sup.3/g.
[0149] The pore size distribution of the disclosed carbon particles
is one parameter that may have an effect on the electrochemical
performance of the blends. Accordingly, in one embodiment, the
carbon particles comprise a fractional pore volume of pores at or
below 100 nm that comprises at least 50% of the total pore volume,
at least 75% of the total pore volume, at least 90% of the total
pore volume or at least 99% of the total pore volume. In other
embodiments, the carbon particle comprises a fractional pore volume
of pores at or below 20 nm that comprises at least 50% of the total
pore volume, at least 75% of the total pore volume, at least 90% of
the total pore volume or at least 99% of the total pore volume.
[0150] In another embodiment, the carbon particles comprise a
fractional pore surface area of pores at or below 100 nm that
comprises at least 50% of the total pore surface area, at least 75%
of the total pore surface area, at least 90% of the total pore
surface area or at least 99% of the total pore surface area. In
another embodiment, the carbon particles comprise a fractional pore
surface area of pores at or below 20 nm that comprises at least 50%
of the total pore surface area, at least 75% of the total pore
surface area, at least 90% of the total pore surface area or at
least 99% of the total pore surface area.
[0151] In another embodiment, the carbon particles comprise pores
predominantly in the range of 1000 angstroms or lower, for example
100 angstroms or lower, for example 50 angstroms or lower.
Alternatively, the carbon particles comprise micropores in the
range of 0-20 angstroms and mesopores in the range of 20-1000
angstroms. The ratio of pore volume or pore surface in the
micropore range compared to the mesopore range can be in the range
of 95:5 to 5:95.
[0152] In other embodiments, the carbon particles are mesoporous
and comprise monodisperse mesopores. As used herein, the term
"monodisperse" when used in reference to a pore size refers
generally to a span (further defined as (Dv90-Dv10)/Dv, 50 where
Dv10, Dv50 and Dv90 refer to the pore size at 10%, 50% and 90% of
the distribution by volume of about 3 or less, typically about 2 or
less, often about 1.5 or less.
[0153] Yet in other embodiments, the carbons particles comprise a
total pore volume of at least 0.2 cc/g. at least 0.5 cc/g, at least
0.75 cc/g, at least 1 cc/g, at least 2 cc/g, at least 3 cc/g, at
least 4 cc/g or at least 7 cc/g. In one particular embodiment, the
carbon particles comprise a pore volume of from 0.5 cc/g to 1.0
cc/g.
[0154] In other embodiments, the carbon particles comprise at least
50% of the total pore volume residing in pores with a diameter
ranging from 50 .ANG. to 5000 .ANG.. In some instances, the carbon
particles comprise at least 50% of the total pore volume residing
in pores with a diameter ranging from 50 .ANG. to 500 .ANG.. Still
in other instances, the carbon particles comprise at least 50% of
the total pore volume residing in pores with a diameter ranging
from 500 .ANG. to 1000 .ANG.. Yet in other instances, the carbon
particles comprise at least 50% of the total pore volume residing
in pores with a diameter ranging from 1000 .ANG. to 5000 .ANG..
[0155] In some embodiments, the mean particle diameter for the
carbon particles ranges from 1 to 1000 microns. In other
embodiments the mean particle diameter for the carbon particles
ranges from 1 to 100 microns. Still in other embodiments the mean
particle diameter for the carbon particles ranges from 5 to 50
microns. Yet in other embodiments, the mean particle diameter for
the carbon particles ranges from 5 to 15 microns or from 3 to 5
microns. Still in other embodiments, the mean particle diameter for
the carbon particles is about 10 microns.
[0156] In some embodiments, the carbon particles comprise pores
having a peak pore volume ranging from 2 nm to 10 nm. In other
embodiments, the peak pore volume ranges from 10 nm to 20 nm. Yet
in other embodiments, the peak pore volume ranges from 20 nm to 30
nm. Still in other embodiments, the peak pore volume ranges from 30
nm to 40 nm. Yet still in other embodiments, the peak pore volume
ranges from 40 nm to 50 nm. In other embodiments, the peak pore
volume ranges from 50 nm to 100 nm.
[0157] While not wishing to be bound by theory, a carbon particle
comprising small pore sizes (i.e., pore lengths) may have the
advantage of decreased diffusion distances to facilitate
impregnation of lead or a lead salt. For example, it is believed
that the employment of carbon particles with a substantial fraction
of pores in the mesopore range (as discussed above) will provide a
significant advantage compared to carbon particles which comprise
much larger pore sizes, for example micron or millimeter size
pores.
[0158] In some embodiments, the blend comprises carbon particles
and lead particles wherein, the carbon particles exhibit low
surface functionality. For example, in some embodiments, the carbon
particles exhibit a surface functionality of less than 20 mEq per
100 gram of carbon, less than 10 mEq per 100 gram of carbon, less
than 5 mEq per 100 gram of carbon as determined by Boehm titration
or less than 1 mEq per 100 gram of carbon as determined by Boehm
titration. In other embodiments, the carbon particles exhibit a
surface functionality of greater than 20 mEq per 100 gram of carbon
as determined by Boehm titration.
[0159] The acidity of the carbon particles may also vary. In some
embodiments, acidity, basicity or neutrality of the carbon
particles can be determined by adding the carbon particles to
sulfuric acid and measuring a change in pH. If the pH decreases,
the carbon particles are acidic. If the pH increases, the carbon
particles are basic. If the pH shows no change, the carbon
particles are neutral. The present invention includes individual
embodiments wherein the carbon particles are acidic, basic or
neutral. The following table shows different carbon embodiments
having different pH values and change in molarity values (see e.g.,
Example 32)
TABLE-US-00001 pH Range Change in Molarity Range 3.5-4.5 0 to -0.25
3.5 to 4.5.sup. -0.5 to -0.75 5 to 6.5 0.3 to 0.8 7.5 to 9 0.25 to
0.6 8 to 9.5 0 to -0.25 8 to 9.5 -0.1 to -1.3
[0160] The pH of the carbon particles can vary. For example, in
some embodiments the pH of the carbon particles is basic. For
example, in some embodiments the pH of the carbon particles is
greater than 7, greater than 8 or greater than 9. In other
embodiments, the pH of the carbon particles is acidic. For example,
in certain embodiments the pH of the carbon particles is less than
7, less than 6 or less than 5. In still other embodiments, the pH
of the carbon particles may be determined by suspending the carbon
particles in water and measuring the resulting pH.
[0161] The blend may comprise a plurality of carbon particles and a
plurality of lead particles, wherein the capacitance of the carbon
particles varies. In some embodiments, the capacitance of the
carbon particles measured at a rate of 1 mA is greater than 600
F/g, greater than 550 F/g, greater than 500 F/g, greater than 450
F/g, greater than 400 F/g, greater than 350 F/g, greater than 300
F/g, greater than 250 F/g, greater than 200 F/g or greater than 100
F/g. In other embodiments, the capacitance of the carbon particles
measured at a rate of 1 mA is less than 300 F/g or less than 250
F/g. In certain embodiments of the foregoing, the capacitance is
measured in a sulfuric acid electrolyte. For example, in some
embodiments the capacitance is measured based on the discharge data
of a galvanostatic charge/discharge profile to 0.9V and 0V at a
symmetric current density ranging from 0.1 A/g carbon to 10 A/g
carbon (see e.g., Example 28).
[0162] In certain embodiments, the water absorbing properties
(i.e., total amount of water the carbon particles can absorb) of
the carbon particles are predictive of the carbon's electrochemical
performance when incorporated into a carbon-lead blend. The water
can be absorbed into the pore volume in the carbon particles and/or
within the space between the individual carbon particles. The more
water absorption, the greater the surface area is exposed to water
molecules, thus increasing the available lead-sulfate nucleation
sites at the liquid-solid interface. The water accessible pores
also allow for the transport of electrolyte into the center of the
lead pasted plate for additional material utilization. Accordingly,
in some embodiments the carbon particles are activated carbon
particles and have a water absorption of greater than 0.2 g
H.sub.2O/cc (cc=pore volume in the carbon particle), greater than
0.4 g H.sub.2O/cc, greater than 0.6 g H.sub.2O/cc, greater than 0.8
g H.sub.2O/cc, greater than 1.0 g H.sub.2O/cc, greater than 1.25 g
H.sub.2O/cc, greater than 1.5 g H.sub.2O/cc, greater than 1.75 g
H.sub.2O/cc, greater than 2.0 g H.sub.2O/cc, greater than 2.25 g
H.sub.2O/cc, greater than 2.5 g H.sub.2O/cc or even greater than
2.75 g H.sub.2O/cc. In other embodiments the particles are
unactivated particles and have a water absorption of greater than
0.2 g H.sub.2O/cc, greater than 0.4 g H.sub.2O/cc, greater than 0.6
g H.sub.2O/cc, greater than 0.8 g H.sub.2O/cc, greater than 1.0 g
H.sub.2O/cc, greater than 1.25 g H.sub.2O/cc, greater than 1.5 g
H.sub.2O/cc, greater than 1.75 g H.sub.2O/cc, greater than 2.0 g
H.sub.2O/cc, greater than 2.25 g H.sub.2O/cc, greater than 2.5 g
H.sub.2O/cc or even greater than 2.75 g H.sub.2O/cc. Methods for
determining water absorption of exemplary carbon particles are
known in the art and described in Example 26.
[0163] The water absorption of the carbon particles can also be
measured in terms of an R factor, wherein R is the maximum grams of
water absorbed per gram of carbon. In some embodiments, the R
factor is greater than 2.0, greater than 1.8, greater than 1.6,
greater than 1.4, greater than 1.2, greater than 1.0, greater than
0.8, or greater than 0.6. In other embodiments, the R value ranges
from 1.2 to 1.6, and in still other embodiments the R value is less
than 1.2.
[0164] The R factor of a carbon particle can also be determined
based upon the carbon particles' ability to absorb water when
exposed to a humid environment for extended periods of time (e.g.,
2 weeks). For example, in some embodiments the R factor is
expressed in terms of relative humidity. In this regard, the carbon
particles comprise an R factor ranging from about 0.1 to about 1.0
at relative humidities ranging from 10% to 100%. In some
embodiments, the R factor is less than 0.1, less than 0.2, less
than 0.3, less than 0.4, less than 0.5, less than 0.6, less than
0.7 or even less than 0.8 at relative humidities ranging from 10%
to 100%. In embodiments of the foregoing, the carbon particles
comprise a total pore volume between about 0.1 cc/g and 2.0 cc/g,
between about 0.2 cc/g and 1.8 cc/g, between about 0.4 cc/g and 1.4
cc/g, between about 0.6 cc/g and 1.2 cc/g. In other embodiments of
the foregoing, the relative humidity ranges from about 10% to about
20%, from about 20% to about 30%, from about 30% to about 40%, from
about 40% to about 50%, from about 50% to about 60%, from about
60%, to about 70%, from about 70% to about 80%, from about 80% to
about 90% or from about 90% to about 99% or even 100%. The above R
factors may be determined by exposing the carbon particles to the
specified humidities at room temperature for two weeks.
[0165] In another embodiment of the present disclosure, the carbon
particles are prepared by a method disclosed herein, for example,
in some embodiments the carbon particles are prepared by a method
comprising pyrolyzing a dried polymer gel as disclosed herein. In
some embodiments, the pyrolyzed polymer gel is further activated to
obtain an activated carbon material. In some embodiments, the
activated carbon material is particle size reduced using approaches
known in the art, for example, jet milling or ball milling. Carbon
particles comprising lead can also be prepared by any number of
methods described in more detail below.
C. Preparation of the Blends
[0166] Blends of carbon particles and lead particles can be
produced by methods known in the art. In general, the blends are
prepared by admixing carbon particles and lead particles and
optionally an electrolyte, expander, binder or combinations
thereof. For example, particles of carbon can be made by the
polymer gel methods disclosed herein and in U.S. application Ser.
No. 12/965,709 and U.S. Publication No. 2001/002086, both of which
are hereby incorporated by reference in their entireties. Particles
of lead can be made by methods known in the art, for example
milling, grinding and the like. Blending of the two different
particles can be accomplished also by methods known. In the case of
blending multiple populations of carbon particles with lead
particles, blending can be done preferentially or in bulk. For
example, two particle populations can be initially blended and a
third can be added to this mixture. In one embodiment, this first
mixture exhibits bimodal carbon particle size. In a further
embodiment, the first mixture represents a bimodal distribution of
carbon particles and lead particles. In a further embodiment, the
first mixture represents a mixture of carbon particles and lead
particles of similar size. Details for preparation of the carbon
particles are described below.
[0167] 1. Preparation of Polymer Gels
[0168] The polymer gels may be prepared by a sol gel process. For
example, the polymer gel may be prepared by co-polymerizing one or
more polymer precursors in an appropriate solvent. In one
embodiment, the one or more polymer precursors are co-polymerized
under acidic conditions. In some embodiments, a first polymer
precursor is a phenolic compound and a second polymer precursor is
an aldehyde compound. In one embodiment, of the method the phenolic
compound is phenol, resorcinol, catechol, hydroquinone,
phloroglucinol, or a combination thereof; and the aldehyde compound
is formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde,
benzaldehyde, cinnamaldehyde, or a combination thereof. In a
further embodiment, the phenolic compound is resorcinol, phenol or
a combination thereof, and the aldehyde compound is formaldehyde.
In yet further embodiments, the phenolic compound is resorcinol and
the aldehyde compound is formaldehyde.
[0169] In certain embodiments, lead may be incorporated during the
above described polymerization process. For example, in some
embodiments, lead in the form of lead particles, lead paste, lead
salt, lead oxide or molten lead can be dissolved or suspended into
the mixture from which the gel resin is produced. In some specific
embodiments, the lead is in the form of a lead salt. Examples of
lead salts in this context include, but are not limited to: lead
acetate, lead orthoarsenate, lead pyroarsenate, lead bromide, lead
caprate, lead carproate, lead caprylate, lead chlorate, lead
chloride, lead fluoride, lead monooxide, lead nitrate, lead
oxychloride, lead orthophosphate sulfate, lead sulfide, and lead
tungstate. Combinations of the above lead salts may also be
employed.
[0170] In some embodiments, the lead salt dissolved into the
mixture from which the gel resin is produced is soluble in the
reaction mixture. In this case, the mixture from which the gel
resin is produced may contain an acid and/or alcohol which improves
the solubility of the lead salt. The lead-containing polymer gel
can be freeze dried, followed by pyrolysis and activation to result
in lead-containing activated carbon suitable for use in hybrid
carbon/metal energy storage devices as discussed in more detail
below.
[0171] The sol gel polymerization process is generally performed
under catalytic conditions. Accordingly, in some embodiments,
preparing the polymer gel comprises co-polymerizing one or more
polymer precursors in the presence of a catalyst. In some
embodiments, the catalyst comprises a basic volatile catalyst. For
example, in one embodiment, the basic volatile catalyst comprises
ammonium carbonate, ammonium bicarbonate, ammonium acetate,
ammonium hydroxide, or combinations thereof. In a further
embodiment, the basic volatile catalyst is ammonium carbonate. In
another further embodiment, the basic volatile catalyst is ammonium
acetate.
[0172] The molar ratio of catalyst to phenolic compound may have an
effect on the final properties of the polymer gel as well as the
final properties of the carbon materials, for example. Thus, in
some embodiments such catalysts are used in the range of molar
ratios of 5:1 to 2000:1 phenolic compound:catalyst. In some
embodiments, such catalysts can be used in the range of molar
ratios of 20:1 to 200:1 phenolic compound:catalyst. For example in
other embodiments, such catalysts can be used in the range of molar
ratios of 5:1 to 100:1 phenolic compound:catalyst.
[0173] The reaction solvent is another process parameter that may
be varied to obtain the desired properties (e.g., surface area,
porosity, purity, etc.) of the polymer gels and carbon materials.
In some embodiments, the solvent for preparation of the polymer gel
is a mixed solvent system of water and a miscible co-solvent. For
example, in certain embodiments the solvent comprises a water
miscible acid. Examples of water miscible acids include, but are
not limited to, propionic acid, acetic acid, and formic acid. In
further embodiments, the solvent comprises a ratio of
water-miscible acid to water of 99:1, 90:10, 75:25, 50:50, 25:75,
10:90 or 1:90. In other embodiments, acidity is provided by adding
a solid acid to the reaction solvent.
[0174] In some other embodiments of the foregoing, the solvent for
preparation of the polymer gel is acidic. For example, in certain
embodiments the solvent comprises acetic acid. For example, in one
embodiment, the solvent is 100% acetic acid. In other embodiments,
a mixed solvent system is provided, wherein one of the solvents is
acidic. For example, in one embodiment of the method the solvent is
a binary solvent comprising acetic acid and water. In further
embodiments, the solvent comprises a ratio of acetic acid to water
of 99:1, 90:10, 75:25, 50:50, 25:75, 20:80, 10:90 or 1:90. In other
embodiments, acidity is provided by adding a solid acid to the
reaction solvent.
[0175] In some embodiments, the lead is incorporated into the
polymer gel after the polymerization step, for example either
before or after drying of the polymer gel. In some other
embodiments, the polymer gel (either before or after drying) is
impregnated with lead by immersion in a lead salt solution or
suspension. The lead salt solution or suspension may comprise acids
and/or alcohols to improve solubility of the lead salt. Lead salts
in this context include, but are not limited to, those described
above. In yet another variation, the polymer gel (either before or
after drying) is contacted with a paste comprising lead. In yet
another variation, the polymer gel (either before or after drying)
is contacted with lead or a lead oxide sol. The sol is a nanophase
colloidal suspension which is maintained using control over pH and
liquid solid interfacial properties such as surface tension,
polarity, and solvent solid interactions.
[0176] In some embodiments, the polymerization is conducted to
produce a single continuous phase that is used to form a monolithic
resin after curing. In other embodiments, the polymerization is
conducted in a two or more phase system, wherein the aqueous
polymer containing phase is cured in particulate form.
[0177] Some embodiments of the disclosed method do not comprise a
solvent exchange step (e.g., exchange t-butanol for water) prior to
drying (e.g., lyophilization). For example, in one embodiment of
any of the methods described herein, before freezing, the polymer
gel or polymer gel particles are rinsed with water. In one
embodiment, the average diameter of the polymer gel particles prior
to freezing is less than 25 mm, for example, between 0.001 mm and
25 mm; alternately, the average diameter of the polymer gel
particles prior to freezing is between 0.01 mm and 15 mm, for
example, between 1.0 mm and 15 mm. In some examples, the polymer
gel particles are between 1 mm and 10 mm. In further embodiments,
the polymer gel particles are frozen via immersion in a medium
having a temperature of below about -10.degree. C., for example,
below about -20.degree. C., or alternatively below about
-30.degree. C. For example, the medium may be liquid nitrogen or
ethanol (or other organic solvent) in dry ice or ethanol cooled by
another means. In some embodiments, drying under vacuum comprises
subjecting the frozen particles to a vacuum pressure of below about
1400 mTorr.
[0178] Other methods of rapidly freezing the polymer gel particles
are also envisioned. For example, in another embodiment the polymer
gel is rapidly frozen by co-mingling or physical mixing of polymer
gel particles with a suitable cold solid, for example, dry ice
(solid carbon dioxide). Another envisioned method comprises using a
blast freezer with a metal plate at -60.degree. C. to rapidly
remove heat from the polymer gel particles scattered over its
surface. Another method of rapidly cooling water in a polymer gel
particle is to snap freeze the particle by pulling a high vacuum
very rapidly (the degree of vacuum is such that the temperature
corresponding to the equilibrium vapor pressure allows for
freezing). Yet another method for rapid freezing comprises admixing
a polymer gel with a suitably cold gas. In some embodiments the
cold gas may have a temperature below about -10.degree. C. In some
embodiments the cold gas may have a temperature below about
-20.degree. C. In some embodiments the cold gas may have a
temperature below about -30.degree. C. In yet other embodiments,
the gas may have a temperature of about -196.degree. C. For
example, in some embodiments, the gas is nitrogen. In yet other
embodiments, the gas may have a temperature of about -78.degree. C.
For example, in some embodiments, the gas is carbon dioxide.
[0179] In other embodiments, the polymer gel particles are frozen
on a lyophilizer shelf at a temperature of -20.degree. C. or lower.
For example, in some embodiments the polymer gel particles are
frozen on the lyophilizer shelf at a temperature of -30.degree. C.
or lower. In some other embodiments, the polymer gel monolith is
subjected to a freeze thaw cycle (from room temperature to
-20.degree. C. or lower and back to room temperature), physical
disruption of the freeze-thawed gel to create particles, and then
further lyophilization processing. For example, in some
embodiments, the polymer gel monolith is subjected to a freeze thaw
cycle (from room temperature to -30.degree. C. or lower and back to
room temperature), physical disruption of the freeze-thawed gel to
create particles, and then further lyophilization processing.
[0180] In some embodiments of the methods described herein, the
molar ratio of phenolic precursor to catalyst is from about 5:1 to
about 2000:1 or the molar ratio of phenolic precursor to catalyst
is from about 20:1 to about 200:1. In further embodiments, the
molar ratio of phenolic precursor to catalyst is from about 25:1 to
about 100:1. In further embodiments, the molar ratio of phenolic
precursor to catalyst is from about 25:1 to about 50:1. In further
embodiments, the molar ratio of phenolic precursor to catalyst is
from about 100:1 to about 5:1.
[0181] In the specific embodiment wherein one of the polymer
precursors is resorcinol and another polymer precursor is
formaldehyde, the resorcinol to catalyst ratio can be varied to
obtain the desired properties of the resultant polymer gel and
carbon materials. In some embodiments of the methods described
herein, the molar ratio of resorcinol to catalyst is from about
10:1 to about 2000:1 or the molar ratio of resorcinol to catalyst
is from about 20:1 to about 200:1. In further embodiments, the
molar ratio of resorcinol to catalyst is from about 25:1 to about
100:1. In further embodiments, the molar ratio of resorcinol to
catalyst is from about 25:1 to about 50:1. In further embodiments,
the molar ratio of resorcinol to catalyst is from about 100:1 to
about 5:1.
[0182] Polymerization to form a polymer gel can be accomplished by
various means described in the art and may include addition of an
electrochemical modifier. For instance, polymerization can be
accomplished by incubating suitable polymer precursor materials,
and optionally an electrochemical modifier, in the presence of a
suitable catalyst for a sufficient period of time. The time for
polymerization can be a period ranging from minutes or hours to
days, depending on the temperature (the higher the temperature the
faster, the reaction rate, and correspondingly, the shorter the
time required). The polymerization temperature can range from room
temperature to a temperature approaching (but lower than) the
boiling point of the starting solution. For example, the
temperature can range from about 20.degree. C. to about 90.degree.
C. In the specific embodiment wherein one polymer precursor is
resorcinol and one polymer precursor is formaldehyde, the
temperature can range from about 20.degree. C. to about 100.degree.
C., typically from about 25.degree. C. to about 90.degree. C. In
some embodiments, polymerization can be accomplished by incubation
of suitable synthetic polymer precursor materials in the presence
of a catalyst for at least 24 hours at about 90.degree. C.
Generally polymerization can be accomplished in between about 6 and
about 24 hours at about 90.degree. C., for example between about 18
and about 24 hours at about 90.degree. C.
[0183] The polymer precursor materials as disclosed herein include
(a) alcohols, phenolic compounds, and other mono- or polyhydroxy
compounds and (b) aldehydes, ketones, and combinations thereof.
Representative alcohols in this context include straight chain and
branched, saturated and unsaturated alcohols. Suitable phenolic
compounds include polyhydroxy benzene, such as a dihydroxy or
trihydroxy benzene. Representative polyhydroxy benzenes include
resorcinol (i.e., 1,3-dihydroxy benzene), catechol, hydroquinone,
and phloroglucinol. Mixtures of two or more polyhydroxy benzenes
can also be used. Phenol (monohydroxy benzene) can also be used.
Representative polyhydroxy compounds include sugars, such as
glucose, and other polyols, such as mannitol. Aldehydes in this
context include: straight chain saturated aldeydes such as methanal
(formaldehyde), ethanal (acetaldehyde), propanal (propionaldehyde),
butanal (butyraldehyde), and the like; straight chain unsaturated
aldehydes such as ethenone and other ketenes, 2-propenal
(acrylaldehyde), 2-butenal (crotonaldehyde), 3 butenal, and the
like; branched saturated and unsaturated aldehydes; and
aromatic-type aldehydes such as benzaldehyde, salicylaldehyde,
hydrocinnamaldehyde, and the like. Suitable ketones include:
straight chain saturated ketones such as propanone and 2 butanone,
and the like; straight chain unsaturated ketones such as propenone,
2 butenone, and 3-butenone (methyl vinyl ketone) and the like;
branched saturated and unsaturated ketones; and aromatic-type
ketones such as methyl benzyl ketone (phenylacetone), ethyl benzyl
ketone, and the like. The polymer precursor materials can also be
combinations of the precursors described above.
[0184] In some embodiments, one polymer precursor is an
alcohol-containing species and another polymer precursor is a
carbonyl-containing species. The relative amounts of
alcohol-containing species (e.g., alcohols, phenolic compounds and
mono- or poly-hydroxy compounds or combinations thereof) reacted
with the carbonyl containing species (e.g. aldehydes, ketones or
combinations thereof) can vary substantially. In some embodiments,
the ratio of alcohol-containing species to aldehyde species is
selected so that the total moles of reactive alcohol groups in the
alcohol-containing species is approximately the same as the total
moles of reactive carbonyl groups in the aldehyde species.
Similarly, the ratio of alcohol-containing species to ketone
species may be selected so that the total moles of reactive alcohol
groups in the alcohol containing species is approximately the same
as the total moles of reactive carbonyl groups in the ketone
species. The same general 1:1 molar ratio holds true when the
carbonyl-containing species comprises a combination of an aldehyde
species and a ketone species.
[0185] The total solids content in the solution or suspension prior
to polymer gel formation can be varied. The weight ratio of
resorcinol to water is from about 0.05 to 1 to about 0.70 to 1.
Alternatively, the ratio of resorcinol to water is from about 0.15
to 1 to about 0.6 to 1. Alternatively, the ratio of resorcinol to
water is from about 0.15 to 1 to about 0.35 to 1. Alternatively,
the ratio of resorcinol to water is from about 0.25 to 1 to about
0.5 to 1. Alternatively, the ratio of resorcinol to water is from
about 0.3 to 1 to about 0.4 to 1.
[0186] Examples of solvents useful in the preparation of the
polymer gels disclosed herein include but are not limited to water
or alcohols such as, for example, ethanol, t butanol, methanol or
combinations thereof as well as aqueous mixtures of the same. Such
solvents are useful for dissolution of the polymer precursor
materials, for example dissolution of the phenolic compound. In
addition, in some processes such solvents are employed for solvent
exchange in the polymer gel (prior to freezing and drying), wherein
the solvent from the polymerization of the precursors, for example,
resorcinol and formaldehyde, is exchanged for a pure alcohol. In
one embodiment of the present application, a polymer gel is
prepared by a process that does not include solvent exchange.
[0187] Suitable catalysts in the preparation of the polymer gels
include volatile basic catalysts that facilitate polymerization of
the precursor materials into a monolithic polymer. The catalyst can
also comprise various combinations of the catalysts described
above. In embodiments comprising phenolic compounds, such catalysts
can be used in the range of molar ratios of 5:1 to 200:1 phenolic
compound:catalyst. For example, in some specific embodiments such
catalysts can be used in the range of molar ratios of 25:1 to 100:1
phenolic compound:catalyst.
[0188] 2. Creation of Polymer Gel Particles
[0189] A monolithic polymer gel can be physically disrupted to
create smaller particles according to various techniques known in
the art. The resultant polymer gel particles generally have an
average diameter of less than about 30 mm, for example, in the size
range of about 1 mm to about 25 mm, or between about 1 mm to about
5 mm or between about 0.5 mm to about 10 mm. Alternatively, the
size of the polymer gel particles can be in the range below about 1
mm, for example, in the size range of about 10 to 1000 microns.
Techniques for creating polymer gel particles from monolithic
material include manual or machine disruption methods, such as
sieving, grinding, milling, or combinations thereof. Such methods
are well-known to those of skill in the art. Various types of mills
can be employed in this context such as roller, bead, and ball
mills and rotary crushers and similar particle creation equipment
known in the art.
[0190] In a specific embodiment, a roller mill is employed. A
roller mill has three stages to gradually reduce the size of the
gel particles. The polymer gels are generally very brittle and are
not damp to the touch. Consequently they are easily milled using
this approach; however, the width of each stage must be set
appropriately to achieve the targeted final mesh. This adjustment
is made and validated for each combination of gel recipe and mesh
size. Each gel is milled via passage through a sieve of known mesh
size. Sieved particles can be temporarily stored in sealed
containers.
[0191] In one embodiment, a rotary crusher is employed. The rotary
crusher has a screen mesh size of about 1/8.sup.th inch. In another
embodiment, the rotary crusher has a screen mesh size of about
3/8.sup.th inch. In another embodiment, the rotary crusher has a
screen mesh size of about 5/8.sup.th inch. In another embodiment,
the rotary crusher has a screen mesh size of about 3/8.sup.th
inch.
[0192] Milling can be accomplished at room temperature according to
methods well known to those of skill in the art. Alternatively,
milling can be accomplished cryogenically, for example by
co-milling the polymer gel with solid carbon dioxide (dry ice)
particles. In this embodiment, the two steps of (a) creating
particles from the monolithic polymer gel and (b) rapid,
multidirectional freezing of the polymer gel are accomplished in a
single process.
[0193] 3. Rapid Freezing of Polymer Gels
[0194] After the polymer gel particles are formed from the
monolithic polymer gel, freezing of the polymer gel particles may
be accomplished rapidly and in a multi-directional fashion as
described in more detail above. Freezing slowly and in a
unidirectional fashion, for example by shelf freezing in a
lyophilizer, results in dried material having a very low surface
area. Similarly, snap freezing (i.e., freezing that is accomplished
by rapidly cooling the polymer gel particles by pulling a deep
vacuum) also results in a dried material having a low surface area.
As disclosed herein rapid freezing in a multidirectional fashion
can be accomplished by rapidly lowering the material temperature to
at least about -10.degree. C. or lower, for example, -20.degree. C.
or lower, or for example, to at least about -30.degree. C. or
lower. Rapid freezing of the polymer gel particles creates a fine
ice crystal structure within the particles due to widespread
nucleation of ice crystals, but leaves little time for ice crystal
growth. This provides a high specific surface area between the ice
crystals and the hydrocarbon matrix, which is necessarily excluded
from the ice matrix.
[0195] The concept of extremely rapid freezing to promote
nucleation over crystal growth can also be applied to mixed solvent
systems. In one embodiment, as the mixed solvent system is rapidly
cooled, the solvent component that predominates will undergo
crystallization at its equilibrium melting temperature, with
increased concentration of the co-solvent(s) and concomitant
further freezing point depression. As the temperature is further
lowered, there is increased crystallization of the predominant
solvent and concentration of co-solvent(s) until the eutectic
composition is reached, at which point the eutectic composition
undergoes the transition from liquid to solid without further
component concentration or product cooling until complete freezing
is achieved. In the specific case of water and acetic acid (which
as pure substances exhibit freezing points of 0.degree. C. and
17.degree. C., respectively), the eutectic composition is comprised
of approximately 59% acetic acid and 41% water and freezes at about
-27.degree. C. Accordingly, in one embodiment, the mixed solvent
system is the eutectic composition, for example, in one embodiment
the mixed solvent system comprises 59% acetic acid and 41%
water.
[0196] In one embodiment, freezing slowly and in a unidirectional
fashion can be employed to intentionally modulate the surface area
in the gel after lyophilization, in order to obtained the desired
pore structure in the freeze dried gel.
[0197] 4. Drying of Polymer Gels
[0198] In one embodiment, the frozen polymer gel particles
containing a fine ice matrix are lyophilized under conditions
designed to avoid collapse of the material and to maintain fine
surface structure and porosity in the dried product. Generally
drying is accomplished under conditions where the temperature of
the product is kept below a temperature that would otherwise result
in collapse of the product pores, thereby enabling the dried
material to retain an extremely high surface area.
[0199] The structure of the final carbon material is reflected in
the structure of the dried polymer gel which in turn is established
by the polymer gel properties. These features can be created in the
polymer gel using a sol-gel processing approach as described
herein, but if care is not taken in removal of the solvent, then
the structure is not preserved. It is of interest to both retain
the original structure of the polymer gel and modify its structure
with ice crystal formation based on control of the freezing
process. In some embodiments prior to drying, the aqueous content
of the polymer gel is in the range of about 50% to about 99%. In
certain embodiments upon drying, the aqueous content of the polymer
cryogel is about 10%, alternately less than about 5% or less than
about 2.5%.
[0200] A lyophilizer chamber pressure of about 2250 microns results
in a primary drying temperature in the drying product of about
-10.degree. C. Drying at about 2250 micron chamber pressure or
lower case provides a product temperature during primary drying
that is no greater than about -10.degree. C. As a further
illustration, a chamber pressure of about 1500 microns results in a
primary drying temperature in the drying product of about
-15.degree. C. Drying at about 1500 micron chamber pressure or
lower provides a product temperature during primary drying that is
no greater than about -15.degree. C. As yet a further illustration,
a chamber pressure of about 750 microns results in a primary drying
temperature in the drying product of about -20.degree. C. Drying at
750 micron chamber pressure or lower provides a product temperature
during primary drying that is no greater than about -20.degree. C.
As yet a further illustration, a chamber pressure of about 300
microns results in a primary drying temperature in the drying
product of about -30.degree. C. Drying at 300 micron chamber
pressure or lower provides a product temperature during primary
drying that is no greater than about -30.degree. C.
[0201] In some embodiments, lead is incorporated into the carbon
material after drying of the polymer gel. For example, lead can be
incorporated into the dried polymer gel by contacting the dried
polymer gel with lead, for example, colloidal lead, lead salt, lead
paste, lead oxide or other sources of lead. In some specific
embodiments, lead is incorporated into the dried polymer gel by
contacting the dried polymer gel with a lead salt in a manner and
for a time sufficient to allow diffusion of the lead salt into the
pores of the dried polymer gel. Lead salts useful in this context
include those lead salts described above.
[0202] 5. Pyrolysis and Activation of Polymer Gels
[0203] The polymer gels described above, can be further processed
to obtain carbon materials. Such processing includes, for example,
pyrolysis and/or activation. Generally, in the pyrolysis process,
dried polymer gels are weighed and placed in a rotary kiln. The
temperature ramp is set at 5.degree. C. per minute, the dwell time
and dwell temperature are set; cool down is determined by the
natural cooling rate of the furnace. The entire process is usually
run under an inert atmosphere, such as a nitrogen environment.
Pyrolyzed samples are then removed and weighed. Other pyrolysis
processes are well known to those of skill in the art.
[0204] In some embodiments, lead is incorporated into the carbon
material after pyrolysis of the dried polymer gel. For example,
lead can be incorporated into the pyrolyzed polymer gel by
contacting the pyrolyzed polymer gel with lead, for example,
colloidal lead, molten lead, lead salt, lead paste, lead oxide or
other sources of lead. In some specific embodiments, the lead is
incorporated into the pyrolyzed polymer gel by contacting the
pyrolyzed polymer gel with a lead salt in a manner and for a time
sufficient to allow diffusion of the lead salt into the pores of
the pyrolyzed polymer gel. Lead salts useful in this context
include those lead salts described above.
[0205] In some embodiments, pyrolysis dwell time (the period of
time during which the sample is at the desired temperature) is from
about 0 minutes to about 120 minutes, from about 0 minutes to about
60 minutes, from about 0 minutes to about 30 minutes, from about 0
minutes to about 10 minutes, from about 0 to 5 minutes or from
about 0 to 1 minute.
[0206] Pyrolysis may also be carried out more slowly than described
above. For example, in one embodiment the pyrolysis is carried out
in about 120 to 480 minutes. In other embodiments, the pyrolysis is
carried out in about 120 to 240 minutes.
[0207] In some embodiments, pyrolysis dwell temperature ranges from
about 500.degree. C. to 2400.degree. C. In some embodiments,
pyrolysis dwell temperature ranges from about 650.degree. C. to
1800.degree. C. In other embodiments pyrolysis dwell temperature
ranges from about 700.degree. C. to about 1200.degree. C. In other
embodiments pyrolysis dwell temperature ranges from about
800.degree. C. to about 1000.degree. C. In other embodiments
pyrolysis dwell temperature ranges from about 850.degree. C. to
about 950.degree. C. In other embodiments pyrolysis dwell
temperature is about 900.degree. C.
[0208] In still other embodiments, pyrolysis dwell temperature
ranges from about 500.degree. C. to about 750.degree. C., or from
about 550.degree. C. to about 650.degree. C. In other embodiments
pyrolysis dwell temperature is about 650.degree. C.
[0209] In some embodiments, the pyrolysis dwell temperature is
varied during the course of pyrolysis. In one embodiment, the
pyrolysis is carried out in a rotary kiln with separate, distinct
heating zones. The temperature for each zone is sequentially
decreased from the entrance to the exit end of the rotary kiln
tube. In one embodiment, the pyrolysis is carried out in a rotary
kiln with separate distinct heating zones, and the temperature for
each zone is sequentially increased from entrance to exit end of
the rotary kiln tube.
[0210] Activation time and activation temperature both have a large
impact on the performance of the resulting activated carbon
material, as well as the manufacturing cost thereof. Increasing the
activation temperature and the activation dwell time results in
higher activation percentages, which generally correspond to the
removal of more material compared to lower temperatures and shorter
dwell times. Activation temperature can also alter the pore
structure of the carbon where lower temperatures result in more
microporous carbon and higher temperatures result in mesoporosity.
This is a result of the activation gas diffusion limited reaction
that occurs at higher temperatures and reaction kinetic driven
reactions that occur at lower temperature. Higher activation
percentage often increases performance of the final activated
carbon, but it also increases cost by reducing overall yield.
Improving the level of activation corresponds to achieving a higher
performance product at a lower cost.
[0211] Pyrolyzed polymer gels may be activated by contacting the
pyrolyzed polymer gel with an activating agent. Many gases are
suitable for activating, for example gases which contain oxygen.
Non-limiting examples of activating gases include carbon dioxide,
carbon monoxide, steam, oxygen and combinations thereof. Activating
agents may also include corrosive chemicals such as acids, bases or
salts (e.g., phosphoric acid, acetic acid, citric acid, formic
acid, oxalic acid, uric acid, lactic acid, potassium hydroxide,
sodium hydroxide, zinc chloride, etc.). Other activating agents are
known to those skilled in the art.
[0212] In some embodiments, the activation time is between 1 minute
and 48 hours. In other embodiments, the activation time is between
1 minute and 24 hours. In other embodiments, the activation time is
between 5 minutes and 24 hours. In other embodiments, the
activation time is between 1 hour and 24 hours. In further
embodiments, the activation time is between 12 hours and 24 hours.
In certain other embodiments, the activation time is between 30 min
and 4 hours. In some further embodiments, the activation time is
between 1 hour and 2 hours.
[0213] Pyrolyzed polymer gels may be activated using any number of
suitable apparatuses known to those skilled in the art, for
example, fluidized beds, rotary kilns, elevator kilns, roller
hearth kilns, pusher kilns, etc. In one embodiment of the
activation process, samples are weighed and placed in a rotary
kiln, for which the automated gas control manifold is set to ramp
at a 20.degree. C. per minute rate. Carbon dioxide is introduced to
the kiln environment for a period of time once the proper
activation temperature has been reached. After activation has
occurred, the carbon dioxide is replaced by nitrogen and the kiln
is cooled down. Samples are weighed at the end of the process to
assess the level of activation. Other activation processes are well
known to those of skill in the art. In some of the embodiments
disclosed herein, activation temperatures may range from
800.degree. C. to 1300.degree. C. In another embodiment, activation
temperatures may range from 800.degree. C. to 1050.degree. C. In
another embodiment, activation temperatures may range from about
850.degree. C. to about 950.degree. C. One skilled in the art will
recognize that other activation temperatures, either lower or
higher, may be employed.
[0214] The degree of activation is measured in terms of the mass
percent of the pyrolyzed dried polymer gel that is lost during the
activation step. In one embodiment of the methods described herein,
activating comprises a degree of activation from 5% to 90%; or a
degree of activation from 10% to 80%; in some cases activating
comprises a degree of activation from 40% to 70%, or a degree of
activation from 45% to 65%.
[0215] In some embodiments, lead is incorporated into the carbon
material after activation of the pyrolyzed polymer gel. For
example, lead can be incorporated into the activated carbon
material by contacting the activated carbon material with lead, for
example, molten lead, colloidal lead, lead salt, lead paste, lead
oxide or other sources of lead. In some specific embodiments, the
lead is incorporated into the pyrolyzed polymer gel by contacting
the activated carbon material with a lead salt in a manner and for
a time sufficient to allow diffusion of the lead salt into the
pores of activated carbon material. Lead salts useful in this
context include those lead salts described above.
[0216] In one embodiment, micropores, mesopores and macropores of
the carbon particles contain lead. In another, related embodiment,
both micropores, mesopores and macropores of the carbon particles
are impregnated with lead. The lead is then preferentially washed
from the mesopores and macropores resulting in carbon particle
comprising lead predominantly present in the micropores. In another
embodiment, impregnation of the carbon particles with lead is
carried out under mild conditions such that the mesopores are
impregnated with lead (but no substantial impregnation into
micropores) resulting in a material comprising lead predominantly
present in mesopores.
[0217] Examples of forms of carbon that can be impregnated with
lead as described above are not limited to carbon materials
prepared by a sol gel process. Such forms of carbon include, but
are not limited to: carbon monoliths, carbon particles, carbon
nanotubes, and carbon fibers. The carbon can be present in more
than one form, for example a combination of carbon particles and
carbon monoliths, or carbon particles and carbon fibers. The
employment of a combination of different forms of carbon may
facilitate binding of lead into the carbon matrix. In some
embodiments, a carbon monolith may be formed from a polymer gel
prepared in the presence of carbon fibers, with the purpose of
retention of the monolith upon freezing, drying, and subsequent
pyrolysis, activation, and optional lead impregnation. In another
embodiment, bulking and/or glass-forming agents are incorporated
into the polymer gel such that the monolith is retained upon
freezing, drying, and subsequent pyrolysis, activation, and
optional impregnation with lead. Examples of bulking and/or
glass-forming agents in this context include, but are not limited
to: sugars and poly(ols) such as sucrose and mannitol, and linear
or branched polymers such as poly(ethylene glycol)s and
dextran.
D. Characterization of Polymer Gels and Carbon Particles
[0218] The structural properties of the final carbon material and
intermediate polymer gels may be measured using Nitrogen sorption
at 77K, a method known to those of skill in the art. The final
performance and characteristics of the finished carbon material is
important, but the intermediate products (both dried polymer gel
and pyrolyzed, but not activated, polymer gel), can also be
evaluated, particularly from a quality control standpoint, as known
to those of skill in the art. The Micromeretics ASAP 2020 is used
to perform detailed micropore and mesopore analysis, which reveals
a pore size distribution from 0.35 nm to 50 nm in some embodiments.
The system produces a nitrogen isotherm starting at a pressure of
10.sup.-7 atm, which enables high resolution pore size
distributions in the sub 1 nm range. The software generated reports
utilize a Density Functional Theory (DFT) method to calculate
properties such as pore size distributions, surface area
distributions, total surface area, total pore volume, and pore
volume within certain pore size ranges.
[0219] The impurity and lead content of the carbon particles can be
determined by any number of analytical techniques known to those of
skill in the art. One particular analytical method useful within
the context of the present disclosure is proton induced x-ray
emission (PIXE). This technique is capable of measuring the
concentration of elements having atomic numbers ranging from 11 to
92 at low ppm levels. Accordingly, in one embodiment the
concentration of lead, as well as all other elements, present in
the carbon particles or blends is determined by PIXE analysis.
E. Devices Comprising the Blends
[0220] The disclosed blends can be used as electrode material in
any number of electrical energy storage and distribution devices.
One such device is a hybrid carbon/metal battery, for example a
carbon/lead acid battery. The high purity, surface area and
porosity of the blends impart improved electrical properties to
electrodes prepared from the same. Accordingly, the present
disclosure provides electrical energy storage devices having longer
active life and improved power performance relative to devices
containing other carbon materials. Specifically, because of the
open-cell, porous network, and relatively small pore size of the
carbon particles, the chemically active material of the positive
and negative electrodes of an electrical energy storage device can
be intimately integrated with the current collectors. The reaction
sites in the chemically active carbon can therefore be close to one
or more conductive carbon structural elements. Thus, electrons
produced in the chemically active material at a particular reaction
site must travel only a short distance through the active material
before encountering one of the many conductive structural elements
of a particular current collector.
[0221] In addition, the porosity of the disclosed carbon particles
provides for a reservoir of electrolyte ions (e.g., sulfate ions)
necessary for the charge and discharge in chemical reactions. The
proximity of the electrolyte ions to the active material is much
closer than in traditional electrodes, and as a result, devices
(e.g., batteries) comprising electrodes incorporating the carbon
material offer both improved specific power and specific energy
values. In other words, these devices, when placed under a load,
sustain their voltage above a predetermined threshold value for a
longer time than devices comprising traditional current collectors
made of lead, graphite plates, activated carbon without lead and
the like.
[0222] The increased specific power values offered by the disclosed
devices also may translate into reduced charging times. Therefore,
the disclosed devices may be suitable for applications in which
charging energy is available for only a limited amount of time. For
instance, in vehicles, a great deal of energy is lost during
ordinary braking. This braking energy may be recaptured and used to
charge a battery of, for example, a hybrid vehicle. The braking
energy, however, is available only for a short period of time
(e.g., while braking is occurring). Thus, any transfer of braking
energy to a battery must occur during braking. In view of their
reduced charging times, the devices of the present invention may
provide an efficient means for storing such braking energy.
[0223] FIG. 1 provides an illustration of an energy storage device
10, according to one embodiment of the present disclosure. Energy
storage device 10 may include various types of batteries. For
example, in one embodiment, energy storage device 10 may include a
lead acid battery. Other battery chemistries, however, may be used,
such as those based on nickel, lithium, sodium-sulfur, zinc, metal
hydrides or any other suitable chemistry or materials that can be
used to provide an electrochemical potential.
[0224] Energy storage device 10 may include a housing 12, terminals
14 (only one shown), and cells 16. Each cell 16 may include one or
more positive plates (i.e., electrodes) 18 and one or more negative
plates 19. In a lead acid battery, for example, positive plates 18
and negative plates 19 may be stacked in an alternating fashion.
Plates 18 and 19 typically comprise an active material in
electrical contact with a current collector. In each cell 16, a bus
bar 20 may be provided to connect positive plates 18 together. A
similar bus bar (not shown) may be included to connect negative
plates 19 together.
[0225] Each cell 16 may be electrically isolated from adjacent
cells by a cell separator 22. Moreover, positive plates 18 may be
separated from negative plates 19 by a plate isolator 23. Both cell
separators 22 and plate isolators 23 may be made from electrically
insulating materials that minimize the risk of two adjacent
electrical conductors shorting together. To enable the free flow of
electrolyte and/or ions produced by electrochemical reactions in
energy storage device 10, however, cell separators 22 and plate
isolators 23 may be made from porous materials or materials
conducive to ionic transport.
[0226] Depending on the chemistry of the energy storage device 10,
each cell 16 will have a characteristic electrochemical potential.
For example, in a lead acid battery used in automotive and other
applications, each cell may have a potential of about 2 volts.
Cells 16 may be connected in series to provide the overall
potential of the battery. As shown in FIG. 1, an electrical
connector 24 may be provided to connect positive bus bar 20 of one
cell 16 to a negative bus bar of an adjacent cell. In this way, six
lead acid cells may be linked together in series to provide a
desired total potential of about 12 volts, for example.
Alternative, electrical configurations may be possible depending on
the type of battery chemistry employed and the total potential
desired.
[0227] Once the total desired potential has been provided using an
appropriate configuration of cells 16, this potential may be
conveyed to terminals 14 on housing 12 using terminal leads 26.
These terminal leads 26 may be electrically connected to any
suitable electrically conductive components present in energy
storage device 10. For example, as illustrated in FIG. 1, terminal
leads 26 may be connected to positive bus bar 20 and a negative bus
bar of another cell 16. Each terminal lead 26 may establish an
electrical connection between a terminal 14 on housing 12 and a
corresponding positive bus bar 20 or negative bus bar (or other
suitable electrically conductive elements) in energy storage device
10.
[0228] Energy storage device 10 may include aqueous or solid
electrolytic materials that at least partially fill a volume
between positive plates 18 and negative plates 19. In a lead acid
battery, for example, the electrolytic material may include an
aqueous solution of sulfuric acid and water. Nickel-based batteries
may include alkaline electrolyte solutions that include a base,
such as potassium hydroxide, mixed with water. It should be noted
that other acids and other bases may be used to form the
electrolytic solutions of the disclosed batteries.
[0229] Electrode plates 18 and 19 may each include a current
collector and an active material disposed on the current collector.
In certain embodiments, the active material of either electrode
plate 18 or 19 or both comprises any of the carbon-lead blends
disclosed herein. In other specific embodiments, the lead is in the
form of elemental lead, lead (II) oxide, lead (IV) oxide or
combinations thereof. In yet other embodiment, the carbon particles
are mesoporous, and in other embodiments the carbon particles are
microporous.
[0230] In other embodiments, the active material of either
electrode plate 18 or 19 or both comprises a paste of lead, lead
(II) oxide, lead (IV) oxide or combinations thereof and comprises a
carbon-lead blend as disclosed herein. While not wishing to be
bound by theory, it is believed that the presence of certain
elements, in combination with the high surface area, porosity and
purity of the carbon particles, is expected to improve the
performance of lead/acid batteries employing traditional lead
pastes when the carbon-lead blends are admixed with the lead paste.
Accordingly, in some embodiments the present disclosure provides a
lead/acid battery, wherein, a blend according to the present
disclosure is admixed with the lead paste of one of the electrode
plates. In yet other embodiment, the carbon particles are
mesoporous, and in other embodiments the carbon particles are
microporous. Other battery chemistries as described above (e.g.,
nickel, lithium, etc.) are expected to benefit from the use of the
disclosed blends and the above described embodiment is not limited
to lead/acid battery chemistries.
[0231] In some other embodiments, the present disclosure provides a
hybrid device comprising one or more battery electrodes and one or
more supercapacitor (i.e., ultracapacitor) electrodes. These
devices comprise improved performance properties compared to known
batteries or known supercapacitors. Supercapacitor electrodes are
described in detail in co-owned U.S. Pat. No. 7,835,136, which is
hereby incorporated in its entirety, and generally comprise a
carbon material, a binder and an electrode and find utility in a
number of electrical storage and distribution devices.
Supercapacitor electrodes of certain embodiments herein may also
comprise a current collector, for example, a current collector
comprising lead.
[0232] The hybrid device may comprise a positive battery electrode
and a negative supercapacitor electrode. For example, in some
embodiments, the positive battery electrode comprises any of the
disclosed blends and the negative supercapacitor electrode
comprises activated carbon. Accordingly, in some embodiments the
positive battery electrode comprises a blend as disclosed herein
and the supercapacitor comprises activated carbon, for example
ultrapure activated carbon.
[0233] In other embodiments of the hybrid device, the
supercapacitor electrode comprises activated carbon, for example,
ultrapure activated carbon. In other devices, the supercapacitor
electrode comprises a blend according to the present disclosure.
For example, the supercapacitor electrode may comprise activated
carbon impregnated with lead, sulfur, oxides thereof or
combinations thereof. Accordingly, in one embodiment the hybrid
device comprises a positive battery electrode comprising a
carbon-lead blend and further comprises a negative supercapacitor
electrode comprising a carbon material or a carbon-lead blend as
disclosed herein.
[0234] The device can comprise lead-based positive electrodes and
one or a plurality of carbon-based negative electrodes. The carbon
can contain lead or a lead salt within the carbon matrix.
Alternatively, both positive and negative electrode components can
contain a carbon component. In this case, either positive or
negative electrode components, or both, can contain lead or a lead
salt in the carbon matrix.
[0235] In another embodiment, the present disclosure provides an
electrical energy storage device comprising:
[0236] a) at least one positive electrode comprising a first active
material in electrical contact with a first current collector;
[0237] b) at least one negative electrode comprising a second
active material in electrical contact with a second current
collector; and
[0238] c) an electrolyte;
[0239] wherein the positive electrode and the negative electrode
are separated by an inert porous separator, and wherein at least
one of the first or second active materials comprises the
carbon-lead blend. In certain embodiments, the device is a battery,
for example, a lead acid battery. Active materials within the scope
of the present disclosure include materials capable of storing
and/or conducting electricity (e.g., an electrochemical
modifier).
[0240] In other embodiments, the electrical energy storage device
comprises one or more lead-based positive electrodes and one or
more carbon-based negative electrodes, and the carbon-based
electrode comprises a carbon-lead blend. In other embodiments of
the disclosed device, both positive and negative electrode
components optionally comprise carbon, for example, a blend as
disclosed herein. For example, either the positive or negative
electrode components, or both, comprise any of the disclosed
blends. In further embodiments of the foregoing, the positive
and/or negative electrodes further comprise one or more other
elements in addition to lead and carbon which act to enhance the
performance of the active materials. Such other elements include,
but are not limited to, lead, tin, antimony, bismuth, arsenic,
tungsten, silver, zinc, cadmium, indium, sulfur, silicon and
combinations thereof as well as oxides of the same and compounds
comprising the same.
[0241] The disclosed blends find utility in electrodes for use in
lead acid batteries. Accordingly, one embodiment of the present
disclosure is a hybrid lead-carbon-acid electrical energy storage
device comprising at least one cell, wherein the at least one cell
comprises a plurality of carbon-lead-based positive electrodes and
one or more carbon-lead-based negative electrodes. The device
further comprises separators between the cells, an acid electrolyte
(e.g., aqueous sulfuric acid), and a casing to contain the
device.
[0242] In some embodiments of the hybrid lead-carbon-acid energy
storage device, each carbon-based negative electrode comprises a
highly conductive current collector; a carbon-lead blend adhered to
and in electrical contact with at least one surface of the current
collector, and a tab element extending above the top edge of the
negative or positive electrode. For example, each carbon-lead-based
positive electrode may comprise a lead-based current collector and
a lead dioxide-based active material paste adhered to, and in
electrical contact with, the surfaces thereof, and a tab element
extending above the top edge of the positive electrode. The lead
dioxide based active material comprises any of the disclosed
blends. The lead or lead oxide in the blend serves as the energy
storing active material for the cathode.
[0243] In other embodiments of the hybrid lead-carbon-acid energy
storage device, the front and back surfaces of a lead-based current
collector each comprise a matrix of raised and lowered portions
with respect to the mean plane of the lead-based current collector,
and further comprises slots formed between the raised and lowered
portions thereof. In this embodiment, the aggregate thickness of
the lead-based current collector is greater than the thickness of
the lead-based material forming the current collector.
[0244] A negative electrode may comprise a conductive current
collector; a carbon-lead blend; and a tab element extending from a
side, for example from above a top edge, of the negative electrode.
Negative electrode tab elements may be electrically secured to one
another by a cast-on strap, which may comprise a connector
structure. The active material may be in the form of a sheet that
is adhered to, and in electrical contact, with the current
collector matrix. In order for the blend to be adhered to and in
electrical contact with the current collector matrix, the blend may
be mixed with a suitable binder substance such as PTFE or ultra
high molecular weight polyethylene (e.g., having a molecular weight
numbering in the millions, usually between about 2 and about 6
million). In some embodiments, the binder material does not exhibit
thermoplastic properties or exhibits minimal thermoplastic
properties.
[0245] In certain embodiments, each battery cell comprises four
positive electrodes which are lead-based and comprise lead dioxide
active material. Each positive electrode comprises a highly
conductive current collector comprising porous carbon material
(e.g., a carbon-lead blend) adhered to each face thereof and lead
dioxide contained within the carbon. Also, in this embodiment, the
battery cell comprises three negative electrodes, each of which
comprises a highly conductive current collector comprising porous
carbon material adhered to each face thereof where this porous
carbon material comprises lead within the carbon.
[0246] In other embodiments, each cell comprises a plurality of
positive electrodes and a plurality of negative electrodes that are
placed in alternating order. Between each adjacent pair of positive
electrodes and the negative electrodes, there is placed a
separator. Each of the positive electrodes is constructed so as to
have a tab extending above the top edge of each respective
electrode; and each of the negative electrodes has a tab extending
above the top edge of each of the respective negative electrodes.
In certain variations, the separators are made from a suitable
separator material that is intended for use with an acid
electrolyte, and that the separators may be made from a woven
material such as a non-woven or felted material, or a combination
thereof. In other embodiments, the material of the current
collector is sheet lead, which may be cast or rolled and punched or
machined.
[0247] Each cell may comprise alternating positive and negative
plates, and an electrolyte may be disposed in a volume between the
positive and negative plates. Additionally, the electrolyte can
occupy some or all of the pore space in the materials included in
the positive and negative plates. In one embodiment, the
electrolyte includes an aqueous electrolytic solution within which
the positive and negative plates may be immersed. The electrolytic
solution composition may be chosen to correspond with a particular
battery chemistry. In lead acid batteries, for example, the
electrolyte may include a solution of sulfuric acid and distilled
water. Other acids, however, may be used to form the electrolytic
solutions of the disclosed batteries.
[0248] In another embodiment, the electrolyte may include a silica
gel. This silica gel electrolyte can be added to the battery such
that the gel at least partially fills a volume between the positive
and negative plate or plates of cell.
[0249] In some other variations, the positive and negative plates
of each cell may include a current collector packed or coated with
a chemically active material. Chemical reactions in the active
material disposed on the current collectors of the battery enable
storage and release of electrical energy. The composition of this
active material, and not the current collector material, determines
whether a particular current collector functions either as a
positive or a negative plate.
[0250] The composition of the chemically active material also
depends on the chemistry of the device. For example, lead acid
batteries may include a chemically active material comprising, for
example, an oxide or salt of lead. In certain embodiments, the
chemically active material may comprise lead dioxide (PbO.sub.2).
The chemically active material may also comprise various additives
including, for example, varying percentages of free lead,
structural fibers, conductive materials, carbon, and extenders to
accommodate volume changes over the life of the battery. In certain
embodiments, the constituents of the chemically active material for
lead acid batteries may be mixed with sulfuric acid and water to
form a paste, slurry, or any other type of coating material.
[0251] The chemically active material in the form of a paste or a
slurry, for example, may be applied to the current collectors of
the positive and negative plates. The chemically active material
may be applied to the current collectors by dipping, painting, or
via any other suitable coating technique.
[0252] In certain embodiments, the positive and negative plates of
a battery are formed by first depositing the chemically active
material on the corresponding current collectors to make the
plates. While not necessary in all applications, in certain
embodiments, the chemically active material deposited on current
collectors may be subjected to curing and/or drying processes. For
example, a curing process may include exposing the chemically
active materials to elevated temperature and/or humidity to
encourage a change in the chemical and/or physical properties of
the chemically active material.
[0253] After assembling the positive and negative plates to form
cells, the battery may be subjected to a charging (i.e., formation)
process. During this charging process, the composition of the
chemically active materials may change to a state that provides an
electrochemical potential between the positive and negative plates
of the cells. For example, in a lead acid battery, the PbO active
material of the positive plate may be electrically driven to lead
dioxide (PbO.sub.2), and the active material of the negative plate
may be converted to sponge lead. Conversely, during subsequent
discharge of a lead acid battery, the chemically active materials
of both the positive and negative plates convert toward lead
sulfate.
[0254] The blends of the presently disclosed embodiments include a
network of pores, which can provide a large amount of surface area
for each current collector. For example, in certain embodiments of
the above described devices the carbon particles are mesoporous,
and in other embodiments the carbon particles are microporous.
Current collectors comprising the blends may exhibit more than 2000
times the amount of surface area provided by conventional current
collectors. Further, a carbon layer may be fabricated to exhibit
any combination of physical properties described above.
[0255] The substrate (i.e., support) for the active material may
include several different material and physical configurations. For
example, in certain embodiments, the substrate may comprise an
electrically conductive material, glass, or a polymer. In certain
embodiments, the substrate may comprise lead or polycarbonate. The
substrate may be formed as a single sheet of material.
Alternatively, the substrate may comprise an open structure, such
as a grid pattern having cross members and struts.
[0256] The substrate may also comprise a tab for establishing an
electrical connection to a current collector. Alternatively,
especially in embodiments where substrate includes a polymer or
material with low electrical conductivity, a carbon layer may be
configured to include a tab of material for establishing an
electrical connection with a current collector. In such an
embodiment, the carbon used to form a tab and the carbon layer may
be infused with a metal such as lead, silver, or any other suitable
metal for aiding in or providing good mechanical and electrical
contact to the carbon layer.
[0257] The blends may be physically attached to the substrate such
that the substrate can provide support for the blend. In one
embodiment, the blend may be laminated to the substrate. For
example, the blend and substrate may be subjected to any suitable
laminating process, which may comprise the application of heat
and/or pressure, such that the blend becomes physically attached to
the substrate. In certain embodiments, heat and/or pressure
sensitive laminating films or adhesives may be used to aid in the
lamination process.
[0258] In other embodiments, the blend may be physically attached
to the substrate via a system of mechanical fasteners. This system
of fasteners may comprise any suitable type of fasteners capable of
fastening a carbon layer to a support. For example, a blend may be
joined to a support using staples, wire or plastic loop fasteners,
rivets, swaged fasteners, screws, etc. Alternatively, a blend can
be sewn to a support using wire thread, or other types of thread.
In some of the embodiments, the blend may further comprise a binder
(e.g., Teflon and the like) to facilitate attachment of the blend
to the substrate.
[0259] In addition to the two-layered current collector (i.e.,
blend plus substrate) described above, the presently disclosed
embodiments include other types of current collectors in
combination with the two-layered current collector. For example,
current collectors suitable for use with the presently disclosed
embodiments may be formed substantially from carbon alone. That is,
a carbon current collector consistent with this embodiment would
lack a support backing. The carbon current collector may, however,
comprise other materials, such as, metals deposited on a portion of
the carbon surface to aid in establishing electrical contact with
the carbon current collector.
[0260] Other current collectors may be formed substantially from an
electrically conductive material, such as lead. The current
collector may be made from lead and may be formed to include a grid
pattern of cross members and struts. In one embodiment, the current
collector may include a radial grid pattern such that struts
intersect cross members at an angle. Current collector may also
include a tab useful for establishing electrical contact to the
current collector.
[0261] In one embodiment, the current collector may be made from
lead and may be formed to include a hexagonal grid pattern.
Specifically, the structural elements of the current collector may
be configured to form a plurality of hexagonally shaped interstices
in a hexagonally close packed arrangement. The current collector
may also include a tab useful for establishing electrical contact
to the current collector.
[0262] Consistent with the present disclosure, cells may be
configured to include several different current collector
arrangements. In one embodiment, one or more negative plates of a
cell may comprise a current collector having a carbon layer
disposed on a substrate. In this embodiment, one or more positive
plates of a cell may include a carbon current collector (e.g., a
carbon layer not including a substrate) or a lead grid current
collector (e.g., a lead grid collector not including a layer of
carbon).
[0263] In another embodiment, one or more positive plates of a cell
may include a current collector comprising a carbon layer deposited
on a substrate. In this embodiment, one or more negative plates of
a cell may include a carbon current collector (e.g., a carbon
collector not including a substrate) or a lead grid current
collector (e.g., a lead grid collector not including a layer of
carbon).
[0264] In yet another embodiment, both one or more negative plates
and one or more positive plates may include a current collector
comprising a carbon layer deposited on a substrate. Thus, in this
embodiment, the two-layered current collector may be incorporated
into both the positive and the negative electrode plates.
[0265] By incorporating the blends into the positive and/or
negative plates of a battery, corrosion of the current collectors
may be suppressed. As a result, batteries consistent with the
present disclosure may offer significantly longer service lives.
Additionally, the disclosed carbon current collectors may be
pliable, and therefore, they may be less susceptible to damage from
vibration or shock as compared to current collectors made from
graphite plates or other brittle materials. Batteries including
carbon current collectors may perform well in vehicular
applications, or other applications, where vibration and shock are
common.
[0266] In another embodiment, the blend for use in the novel carbon
lead energy storage device may also comprise certain metal and
metal oxide additives that enhance electrochemical performance. To
this end, the cathode paste comprising lead and lead oxides can be
mixed intimately with activated carbon particles. Minor additions
of certain other elements such as tin, antimony, bismuth, arsenic,
tungsten, silver, zinc, cadmium, indium, silicon, oxides thereof,
compounds comprising the same or combinations thereof offer the
potential to increase the chemical energy storage efficiency of the
positive active material. Some of these metal elements and their
oxides act to replicate the lead dioxide crystal structure and
provide additional nucleation sites for the charge discharge
processes as well as an additional conductive network within the
lead dioxide active material. These materials can be located within
the pores of the activated carbon and on the carbon surface before
the lead paste is applied. These metals can act as conductivity
aids for the lead dioxide positive active material as well as
increasing the efficiency of the lead dioxide active material
through this increased conductivity network within the cathode. In
certain embodiments, impurities such as arsenic, cobalt, nickel,
iron, chromium and tellurium are minimized in the carbon and the
electrode because they increase oxygen evolution on the cathode
during the charge cycle.
[0267] In other embodiments, the blend does not contain significant
quantities of metallic impurities such as sodium, potassium and
especially calcium, magnesium, barium, strontium, chromium, nickel,
iron and other metals, which form highly insoluble sulfate salts.
These impurities will precipitate inside the pores of the carbon
material and effectively impede its effectiveness. Sodium and
potassium will neutralize an equi-molar amount of hydrogen ions and
render them ineffective.
[0268] In another embodiment of the disclosure, the carbon
particles in the blend for use in the hybrid carbon lead energy
storage device may be structured with a predominance of mesopores,
that is pores from 2 nm to 50 nm in size, that when mixed into the
positive or negative electrodes will enhance the electrochemical
performance. To this end, the cathode paste comprising lead and
lead oxides can be mixed intimately with activated carbon particles
and the anode paste comprising lead can be mixed intimately with
activated carbon particles. These mesoporous carbons offer the
ability to promote fluid electrolyte to fully penetrate the active
material within the electrode. By increasing the fluid penetration
within the electrode structure, the diffusion distances between the
electrolyte ions (e.g., sulfate) and the active material is reduced
and the chemical charge and discharge process can proceed more
efficiently. In addition, the activated carbon used in this
embodiment may also comprise a number of micropores less than 2 nm
in size in conjunction with the mesopores.
[0269] The blends can be integrated into ultracapacitor test cells.
The activated carbons, such as activated carbon cryogels, are
milled to an average particle size of about 10 microns using a
jetmill operating in a nitrogen atmosphere. This fine particle size
enhances particle-to-particle conductivity, as well as enabling the
production of very thin sheet electrodes. The jetmill essentially
grinds the carbon against itself by spinning it inside a disc
shaped chamber propelled by high-pressure nitrogen. As the larger
particles are fed in, the centrifugal force pushes them to the
outside of the chamber; as they grind against each other, the
particles migrate towards the center where they eventually exit the
grinding chamber once they have reached the appropriate
dimensions.
[0270] The capacitance and power output are measured using cyclic
voltametry (CV), chronopotentiometry (CP) and impedance
spectroscopy at various voltages (ranging from 1.0-2.5 V maximum
voltage) and current levels (from 1-10 mA) on a Biologic
electrochemical workstation. The capacitance is calculated from the
discharge curve of the potentiogram using the formula:
C=i/s Equation 1
where i is the current (A) and s=V/t is the voltage rate in V/s.
Since the test capacitor is a symmetric carbon-carbon (C--C)
electrode, the specific capacitance is determined from:
C.sub.s=2C/m.sub.e Equation 2
where m.sub.e is the surface area of a single electrode. The
specific energy and power is determined using:
E s = 1 4 CV max 2 m e Equation 3 P s = E s / 4 ESR Equation 4
##EQU00001##
where C is the measured capacitance V.sub.max is the maximum test
voltage and ESR is the equivalent series resistance obtained from
the voltage drop at the beginning of the discharge.
[0271] The present disclosure also provides an electrode comprising
the disclosed blends, for example for use in an electrical energy
storage and distribution device. In some embodiments, the electrode
comprises a binder and any of the blends described herein. In other
embodiments, the electrode comprises from 0.1%-20% by weight of the
binder. For example, in some embodiments the binder is
polytetrafluoroethylene.
[0272] In still other embodiments, the electrode further comprises
a current collector. For example, in some embodiments the current
collector comprises lead, and in other embodiments the current
collector is in the form of a grid or plate.
[0273] In yet more embodiments, the electrode further comprises an
electrolyte, for example sulfuric acid. In other embodiments, the
electrode further comprises an expander.
[0274] The present inventions also includes use of a device
comprising the disclosed carbon-lead blends for storage and
distribution of electrical energy. For example, in some embodiments
the device is a battery. In other embodiments, the device is in
microhybrid, start-stop hybrid, mild-hybrid vehicle, vehicle with
electric turbocharging, vehicle with regenerative braking, hybrid
vehicle, an electric vehicle, industrial motive power such as
forklifts, electric bikes, golf carts, aerospace applications, a
power storage and distribution grid, a solar or wind power system,
a power backup system such as emergency backup for portable
military backup, hospitals or military infrastructure, and
manufacturing backup or a cellular tower power system.
[0275] The following Examples are offered by way of illustration
and not by way of limitation.
EXAMPLES
[0276] The polymer gels, cryogels, pyrolyzed cryogels and carbon
materials disclosed in the following Examples were prepared
according to the methods disclosed herein and as described in in
co-pending U.S. application Ser. Nos. 12/748,219; 12/897,969;
12/829,282; 13/046,572; 12/965,709; 13/336,975; and 61/585,611,
each of which are hereby incorporated by reference in their
entireties. Chemicals were obtained from commercial sources at
reagent grade purity or better and were used as received from the
supplier without further purification.
[0277] Unless indicated otherwise, the following conditions were
generally employed for preparation of the carbon materials and
precursors. Phenolic compound and aldehyde were reacted in the
presence of a catalyst in a binary solvent system (e.g., water and
acetic acid). The molar ratio of phenolic compound to aldehyde was
typically 0.5 to 1. The reaction was allowed to incubate in a
sealed container at temperatures of up to 85 C for up to 24 h. The
resulting polymer hydrogel contained water, but no organic solvent;
and was not subjected to solvent exchange of water for an organic
solvent, such as t-butanol. The polymer hydrogel monolith was then
physically disrupted, for example by grinding, to form polymer
hydrogel particles having an average diameter of less than about 5
mm. Unless stated otherwise, the particles were then rapidly
frozen, generally by immersion in a cold fluid (e.g., liquid
nitrogen or ethanol/dry ice) and lyophilized. Generally, the
lyophilizer shelf was pre-cooled to -30.degree. C. before loading a
tray containing the frozen polymer hydrogel particles on the
lyophilizer shelf. The chamber pressure for lyophilization was
typically in the range of 50 to 1000 mTorr and the shelf
temperature was in the range of +10 to +25.degree. C.
Alternatively, the shelf temperature can be set lower, for example
in the range of 0 to +10.degree. C. Alternatively, the shelf
temperature can be set higher, for example in the range of 25 to
+100.degree. C. Chamber pressure can be held in the range of 50 to
3000 mTorr. For instance, the chamber pressure can be controlled in
the range of 150 to 300 mTorr.
[0278] The dried polymer hydrogel was typically pyrolyzed by
heating in a nitrogen atmosphere at temperatures ranging from
550-1200.degree. C. for a period of time as specified in the
examples. Activation conditions generally comprised heating a
pyrolyzed polymer hydrogel in a CO.sub.2 atmosphere at temperatures
ranging from 900-1000.degree. C. for a period of time as specified
in the examples. Specific pyrolysis and activation conditions were
as described in the following examples.
[0279] In certain embodiments, impregnation of the carbon particles
with lead was accomplished by including a source of lead in the
polymerization reaction or contacting the carbon particles, or
precursors of the same (e.g., polymer hydrogel, dried polymer
hydrogel, pyrolyzed polymer gel, etc.), with a source of lead as
described more fully above and exemplified below.
Example 1
Preparation of Dried Polymer Gel
[0280] A polymer gel was prepared by polymerization of resorcinol
and formaldehyde (0.5:1) in water and acetic acid (75:25) and
ammonium acetate (RC=25, unless otherwise stated). The reaction
mixture was placed at elevated temperature (incubation at
45.degree. C. for about 6 h followed by incubation at 85.degree. C.
for about 24 h) to allow for gellation to create a polymer gel.
Polymer gel particles were created from the polymer gel and passed
through a 4750 micron mesh sieve. The sieved particles were frozen
by immersion in liquid nitrogen, loaded into a lyophilization tray
at a loading of 3 to 7 g/in.sup.2, and lyophilized. The time to dry
(as inferred from time for product to reach within 2.degree. C. of
shelf temperature) varied with product loading on the lyophilizer
shelf.
[0281] The surface area of the dried polymer gel was examined by
nitrogen surface analysis using a Micrometrics Surface Area and
Porosity Analyzer (model TriStar II). The measured specific surface
area using the BET approach was in the range of about 500 to 700
m.sup.2/g.
[0282] Additional methodologies for preparation of dried polymer
gel can be found in the art. These additional methodologies
include, but are not limited to, spray drying, air drying, freeze
drying using shelf or snap freezing, and freeze drying under
conditions to obtain dried polymer gel with about 200 to 500 m2/g
specific surface area.
Example 2
Preparation of Pyrolyzed Carbon Material from Dried Polymer Gel
[0283] Dried polymer gel prepared according to Example 2 was
pyrolyzed by passage through a rotary kiln at 850.degree. C. with a
nitrogen gas flow of 200 L/h. The weight loss upon pyrolysis was
about 52%-54%.
[0284] The surface area of the pyrolyzed dried polymer gel was
examined by nitrogen surface analysis using a surface area and
porosity analyzer. The measured specific surface area using the
standard BET approach was in the range of about 600 to 700
m.sup.2/g.
[0285] Additional methodologies for preparation of pyrolyzed carbon
can be found in the art. These additional methodologies can be
employed to obtain pyrolyzed carbon with about 100 to 600 m2/g
specific surface area.
Example 3
Production of Activated Carbon
[0286] The pyrolyzed carbon as described in Example 2 was activated
in a rotary kiln (alumina tube with 2.75 in inner diameter) at
900.degree. C. under a CO.sub.2 flow rate of 30 L/min, resulting in
a total weight of about 37%. Subsequently, this material was
further activated at 900.degree. C. in batchwise fashion in a
silica tube (3.75 inch inner diameter) with 15 L/min CO.sub.2 flow
rate, to achieve a final weight loss (compared to the starting
pyrolyzed carbon) of about 42 to 44%.
[0287] The surface area of the dried gel was examined by nitrogen
surface analysis using a surface area and porosity analyzer. The
measured specific surface area using the BET approach was in the
range of about 1600 to 2000 m.sup.2/g.
[0288] Additional methodologies for preparation of activated carbon
can be found in the art. These additional methodologies can be
employed to obtain dried polymer gel with about 100 to 600 m2/g
specific surface area.
Example 4
Micronization of Activated Carbon Via Jet Milling
[0289] The activated ultrapure carbon from Example 3 was jet milled
using a 2 inch diameter jet mill. The conditions were about 0.7 lbs
of ultrapure activated carbon per hour, nitrogen gas flow about 20
scf per min and about 100 psi pressure. The average particle size
after jet milling was about 8 to 10 microns.
[0290] Additional methodologies for preparation of micronized
particles of activated carbon can be found in the art. These
additional methodologies can be employed to obtain micronized
particles with mon- or polydisperse particle size distributions.
These additional methodologies can be employed to obtain micronized
particles with average size of about 1 to 8 microns. These
additional methodologies can be employed to obtain micronized
particles with average size of greater than 8 microns.
Example 5
Purity Analysis of Activated Carbon & Comparison Carbons
[0291] Activated carbon samples prepared according to Example 4
were examined for their impurity content via proton induced x-ray
emission (PIXE). PIXE is an industry-standard, highly sensitive and
accurate measurement for simultaneous elemental analysis by
excitation of the atoms in a sample to produce characteristic
X-rays which are detected and their intensities identified and
quantified. PIXE is capable of detection of all elements with
atomic numbers ranging from 11 to 92 (i.e., from sodium to
uranium).
[0292] The PIXE impurity (Imp.) data for activated carbons as
disclosed herein as well as other activated carbons for comparison
purposes is presented in Table 1. Sample 1, 3, 4 and 5 are
activated carbons prepared according to Example 3, Sample 2 is a
micronized activated carbon prepared according to Example 4,
Samples 6 and 7 are commercially available activated carbon
samples).
[0293] As seen in Table 1, the synthetic activated carbons
according to the instant disclosure have a lower PIXE impurity
content and lower ash content as compared to other known activated
carbon samples.
TABLE-US-00002 TABLE 1 Purity Analysis of Activated Carbon &
Comparison Carbons Impurity Concentration (PPM) Impurity Sample 1
Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Na ND* ND ND
ND ND 353.100 ND Mg ND ND ND ND ND 139.000 ND Al ND ND ND ND ND
63.850 38.941 Si 53.840 92.346 25.892 17.939 23.602 34.670 513.517
P ND ND ND ND ND ND 59.852 S ND ND ND ND ND 90.110 113.504 Cl ND ND
ND ND ND 28.230 9.126 K ND ND ND ND ND 44.210 76.953 Ca 21.090
16.971 6.141 9.299 5.504 ND 119.804 Cr ND ND ND ND ND 4.310 3.744
Mn ND ND ND ND ND ND 7.552 Fe 7.582 5.360 1.898 2.642 1.392 3.115
59.212 Ni 4.011 3.389 0.565 ND ND 36.620 2.831 Cu 16.270 15.951 ND
ND ND 7.927 17.011 Zn 1.397 0.680 1.180 1.130 0.942 ND 2.151 Total
104.190 134.697 35.676 31.010 31.44 805.142 1024.198 (% Ash)
(0.018) (0.025) (<0.007) (0.006) (0.006) (0.13) (0.16) *ND = not
detected by PIXE analysis
Example 6
Preparation of a Dry Carbon Negative Electrode
[0294] 200 mg of activated (BET specific surface area=2380
m.sup.2/g) carbon prepared as described above was weighed out
followed by 6 mg of Teflon tape. These were combined in an agate
mortar and pestel and hand ground together until a homogenous sheet
was obtained. This sheet was continually folded (.about.5 times)
and rolled flat to a thickness of .about.50 micron. A 5/8''
diameter punch was used to punch out a circular disc electrode from
this material.
[0295] The surface area of the rolled electrode material was
examined by nitrogen surface analysis using a Micromeritics Surface
Area and Porosity Analyzer (model Tri Star II). The measured
specific surface area using the BET approach was 2117
m.sup.2/g.
Example 7
Preparation of Carbon Slurry
[0296] 9 mg of poly(vinyldiene fluoride) is weighed out and
dissolved in 20 mL of 1-methyl-2-pyrrolidinone. Approximately 182
mg of carbon black is weighed out and added to the solution above.
This is stirred 25 minutes followed by sonication for 20 minutes.
Finally, approximately 790 mg of the activated carbon of interest
(e.g., prepared according to the examples herein) is added to the
solution while stirring, then allowed to stir for another 25
minutes followed by sonication for another 20 minutes. At this
point the slurry is complete.
Example 8
Preparation of Carbon Slurry Electrodes
[0297] The slurry from Example 10 is spread onto an aluminum foil
current collector (3''.times.6''.times.30 micron) using a doctor
blade and a vacuum-coater apparatus. The wet as-coated electrodes
are placed in an oven set to 85.degree. C. and allowed to dry for
8-12 hours. The dried carbon coated sheets are placed in a furnace
and heated to 195.degree. C. for 90 minutes under vacuum. The
sheets are removed and 5/8'' diameter electrode discs are punched
out of the sheet. The electrodes are weighed and two of similar
masses are assembled into a stainless steel coin cell as the anode
and cathode. DKK cellulose paper is used as the separator material
and 37 wt % sulfuric acid is used as the electrolyte.
Example 9
Electrochemical Measurement of Carbon Capacitance
[0298] The assembled coin-cells from Example 11 are connected to a
potentiostat as a two electrode system. The coin cell is first held
at open circuit for 15 minutes. The cell is then charged at
constant current (10 mA) until a potential of 0.9V (vs. SCE) is
reached. This is held at constant voltage for two minutes before
being discharged at a constant current of -1 mA until a potential
of 0.1V (vs. SCE) is reached. The process is repeated with
discharge currents of -5 mA, -10 mA, -25 mA, -50 mA, and finally
-100 mA. Capacitance data for various carbon samples is presented
in FIG. 2. The data is interpreted as F/g vs. A/g.
Example 10
Ultrapure Carbon Used as Electrode Material in an Electric Double
Layer Capacitor Device
[0299] The ultrapure activated carbon was used as an electrode
material for an electric double later capacitor device. Capacitor
electrodes comprised 99 parts by weight carbon particles (average
particle size 5-15 microns) and 1 part by weight Teflon. The carbon
and Teflon were masticated in a mortar and pestle until the Teflon
was well distributed and the composite had some physical integrity.
After mixing, the composite was rolled out into a flat sheet,
approximately 50 microns thick. Electrode disks, approximately 1.59
cm in diameter, were punched out of the sheet. The electrodes were
placed in a vacuum oven attached to a dry box and heated for 12
hours at 195 C. This removed water adsorbed from the atmosphere
during electrode preparation. After drying, the electrodes were
allowed to cool to room temperature, the atmosphere in the oven was
filled with argon and the electrodes were moved into the dry box
where the capacitors were made.
[0300] A carbon electrode was placed into a cavity formed by a 1
inch (2.54 cm) diameter carbon-coated aluminum foil disk and a 50
micron thick polyethylene gasket ring which had been heat sealed to
the aluminum. A second electrode was then prepared in the same way.
Two drops of electrolyte consisting of 1.8M tetraethylene ammonium
tetrafluoroborate in acetonitrile were added to each electrode.
Each electrode was covered with a 0.825 inch diameter porous
polypropylene separator. The two electrode halves were sandwiched
together with the separators facing each other and the entire
structure was hot pressed together.
Example 11
Ultrapure Carbon Used as Electrode Material in an Electric Double
Layer Capacitor Device
[0301] The device described in Example 13 was subjected to
electrical testing with a potentiostat/function generator/frequency
response analyzer. Capacitance was measured by a constant current
discharge method, consisting of applying a current pulse for a
known duration and measuring the resulting voltage profile over
time. By choosing a given time and ending voltage, the capacitance
was calculated from the following C=It/.DELTA.V, where
C=capacitance, I=current, t=time to reached the desired voltage and
.DELTA.V=the voltage difference between the initial and final
voltages. The specific capacitance based on the weight and volume
of the two carbon electrodes was obtained by dividing the
capacitance by the weight and volume respectively. This data is
reported in Table 2 below for discharge between 2.7 and 1.89V.
TABLE-US-00003 TABLE 2 Summary of Capacitance Performance
Parameters Capacitance Performance Parameters Measured Value
Gravimetric Power * 13.1 W/g Volumetric Power * 8.7 W/cc
Gravimetric Energy * 4.8 Wh/kg Volumetric Energy * 3.2 Wh/liter
Gravimetric Capacitance @ RC = 5 ** 22 F/g Volumetric Capacitance @
RC = 5 ** 15 F/cc Gravimetric Capacitance @ RC = 20
.sup..dagger-dbl. 27 F/g Volumetric Capacitance @ RC = 20
.sup..dagger-dbl. 18 F/cc * By constant current discharge from 2.7
to 1.89 volts with TEATFB in AN, 0.5 second time constant. ** By
constant current discharge from 2.7 to 0.1 V, 5-second time
constant. .sup..dagger-dbl. By constant current discharge from 2.7
to 0.1 V, 20-second time constant.
Example 12
Electrochemical Performance of Electric Double Layer Capacitor
Device with Ultrapure Carbon Activated to a Higher Weight Loss Used
as Electrode Material
[0302] The ultrapure activated carbon was used as an electrode
material for an electric double later capacitor device. For this
specific example, the carbon was activated for a longer time,
corresponding into about a 10% additional weight loss and an
increase in surface area by 27%. The electrode fabrication and
electrochemical testing parameters are similar to those described
above for Example 14 and 13. The data (Table 3) revealed a
significantly increased gravimetric and volumetric power and
energy.
TABLE-US-00004 TABLE 3 Summary of capacitance performance
parameters Capacitance Performance Parameters Measured Value
Gravimetric Power * 24.4 W/g Volumetric Power * 14.2 W/cc
Gravimetric Energy * 8.8 Wh/kg Volumetric Energy * 4.0 Wh/liter
Gravimetric Capacitance @ RC = 5 ** 20 F/g Volumetric Capacitance @
RC = 5 ** 12 F/cc Gravimetric Capacitance @ RC = 20
.sup..dagger-dbl. 25 F/g Volumetric Capacitance @ RC = 20
.sup..dagger-dbl. 14 F/cc * By constant current discharge from 2.7
to 1.89 volts with TEATFB in AN, 0.5 second time constant. ** By
constant current discharge from 2.7 to 0.1 V, 5-second time
constant. .sup..dagger-dbl. By constant current discharge from 2.7
to 0.1 V, 20-second time constant.
Example 13
Electrochemical Performance of Electric Double Layer Capacitor
Device with Ultrapure Carbon Blended from Different Milling
Fractions Loss Used as Electrode Material
[0303] The ultrapure activated carbon was used as an electrode
material for an electric double later capacitor device. For this
specific example, the final carbon product was a result of adding
the milled material that was collected in the usual procedure in
the product collection jar with material that did not deposit into
the jar (but instead was collected in a bag upstream from the
collection jar. In this case, the specific ratio of blending was
about 3:1 (w:w) for milled carbon collected from the collection jar
to milled carbon collected in the bag upstream from the collection
jar. The electrode fabrication and electrochemical testing
parameters are similar to those described above for Example 14 and
13. The data (Table 4) revealed a significantly increased
gravimetric and volumetric power and energy.
TABLE-US-00005 TABLE 4 Summary of capacitance performance
parameters. Capacitance Performance Parameters Measured Value
Gravimetric Power * 28.8 W/g Volumetric Power * 14.4 W/cc
Gravimetric Energy * 7.4 Wh/kg Volumetric Energy * 3.7 Wh/liter
Gravimetric Capacitance @ RC = 5 ** 28 F/g Volumetric Capacitance @
RC = 5 ** 14 F/cc Gravimetric Capacitance @ RC = 20
.sup..dagger-dbl. 29 F/g Volumetric Capacitance @ RC = 20
.sup..dagger-dbl. 14 F/cc * By constant current discharge from 2.7
to 1.89 volts with TEATFB in AN, 0.5 second time constant. ** By
constant current discharge from 2.7 to 0.1 V, 5-second time
constant. .sup..dagger-dbl. By constant current discharge from 2.7
to 0.1 V, 20-second time constant.
Example 14
Device with Lead Acid Electrode and Carbon-Containing Electrode
[0304] An energy storage device is constructed from a lead acid
cathode and a carbon and lead containing anode. The latter is
prepared from a carbon-lead blend as disclosed herein and lead
paste.
[0305] In this embodiment, the anode paste comprising lead and lead
oxides is mixed intimately with the carbon-lead blend. It is
important that carbon is not exposed directly to the electrolyte in
order to minimize oxygen evolution on carbon and subsequent carbon
dioxide formation during discharge which will lead to carbon loss
and anode performance decay. For this reason, it is important that
the carbon be located deep in the anode paste, preferably in the
back half and better in the rear 25% of the anode. Minor additions
of certain metals such as tin, titanium, zirconium, tantalum and
niobium, alloys and oxides thereof are poor electrocatalysts for
oxygen evolution and stable in strong acid environments. These
materials can be located within the pores of the activated carbon
and on the carbon surface before the lead paste is applied. It is
important to exclude the presence of impurities such as arsenic,
cobalt, nickel, iron, antimony and tellurium in the carbon and from
the electrode in general because they increase hydrogen evolution
on the anode during the charge cycle.
[0306] It is important that the activated carbon not contain
metallic impurities such as sodium, potassium and especially
calcium, magnesium, barium, strontium, iron and other metals, which
form highly insoluble sulfate salts. These will precipitate inside
the pores of the carbon and effectively impede its effectiveness.
Sodium and potassium will neutralize an equi-molar amount of
hydrogen ions and render them ineffective.
[0307] Carbon is more conductive than lead and will improve the
performance of the electrode by reducing its overall resistance and
creating a more uniform current distribution.
[0308] If highly pure carbon as described above is present in the
anode paste as concentrations of 1 to 10%, cycle life will improve
by a factor of 2-5 in deep discharge and float charge applications
(50% state of charge). Current and energy efficiency will improve
also.
Example 15
Device with all Electrodes Comprising Lead and Carbon
[0309] An energy storage device is constructed from two electrodes
that both contain lead and carbon containing elements. The
electrodes are prepared by contacting a carbon-lead blend as
disclosed herein with lead paste.
[0310] In this embodiment, the cathode paste comprising lead
dioxide is intimately mixed with activated carbon particles. It is
important that carbon not be exposed directly to the electrolyte to
limit hydrogen evolution on discharge. Additions of chromium,
bismuth and tin to the carbon will limit the hydrogen discharge
rate. Oxygen present in the electrolyte may also react at the
cathode during the discharge cycle. The presence of arsenic,
bismuth, nickel, antimony, selenium, tin and tellurium enhance
oxygen reduction and should be avoided. Cobalt and chromium
suppress oxygen reduction and can be added to the carbon before
mixing in the cathode paste.
[0311] It is important that the activated carbon not contain
metallic impurities such as sodium, potassium and especially
calcium, magnesium, barium, strontium, iron and other metals, which
form highly insoluble sulfate salts. These will precipitate inside
the pores of the carbon and effectively impede its effectiveness.
Sodium and potassium will neutralize an equi-molar amount of
hydrogen ions and render them ineffective.
[0312] Carbon is more conductive than lead dioxide and will improve
the performance of the electrode by reducing its overall resistance
and creating a more uniform current distribution.
[0313] If highly pure carbon as described above is present in the
anode paste as concentrations of 1 to 10%, cycle life will improve
by a factor of 2-5 in deep discharge and float charge applications
(50% state of charge). Current and energy efficiency will improve
also.
Example 16
Impregnation of Activated Carbon with Lead
[0314] In certain embodiments, the blends comprise a plurality of
carbon particles and a plurality of lead particles, and the carbon
particles comprise lead impregnated within the pores of the carbon
particle or on the surface of the carbon particle. Carbon particles
in these embodiments can be prepared according to the following
examples.
[0315] Saturated solutions of lead acetate, lead nitrate, lead
carbonate and lead sulfate in 25:75 acetic acid:water (vol:vol)
were prepared. Activated carbon (300 mg, microporous and
mesoporous) samples prepared according to Example 4 were suspended
in each lead salt solution and shaken overnight at room
temperature. The liquid mixture was then centrifuged and the
supernatant removed. The carbon pellet was washed three times with
deionized water (5 mL) and dried overnight at 45.degree. C. The
lead content of the carbon samples thus prepared was analyzed by
PIXE. The results are tabulated in Table 5 below.
TABLE-US-00006 TABLE 5 Lead Content of Various Activated Carbon
Samples Sample Activated Carbon Type Lead Source Lead Content 8
Microporous Lead (II) acetate 7.892% 9 Mesoporous Lead (II) acetate
6.526% 10 Microporous Lead (II) nitrate 0.294% 11 Mesoporous Lead
(II) nitrate 2.427% 12 Microporous Lead (II) carbonate 1.855% 13
Mesoporous Lead (II) carbonate 1.169% 14 Microporous Lead (II)
sulfate 84.060 ppm 15 Mesoporous Lead (II) sulfate 27.021 ppm
[0316] Both microporous and mesoporous activated carbons were
studied. An example nitrogen sorption isotherm for microporous
carbon is shown in FIG. 3. In this case, the total specific BET
surface area was 1746 m.sup.2/g, and the total pore volume was 0.82
cc/g. From these data, the DFT pore distribution was determined as
shown in FIG. 4. About 50% of the pore volume resides in pores of
less than about 25 {acute over (.ANG.)}. About 50% of the pore
surface area resides in pores of less than 17 {acute over (.ANG.)}.
An example DFT pore distribution for mesoporous carbon is depicted
in FIG. 5. In this case, the total specific BET surface area was
2471 m.sup.2/g, and the total pore volume was 2.05 cc/g. About 50%
of the pore volume resides in pores of less than about 54 {acute
over (.ANG.)}.
[0317] As can be seen from the data in Table 5, for highly soluble
lead salts (such as lead acetate, lead nitrate and lead carbonate)
it was possible to generate carbon materials with substantial
levels of lead in the final material, in the range of 0.3 to 8%. In
the case of lead sulfate, only ppm levels (<100) were achieved
via the impregnation method. Best results were obtained for more
highly soluble lead salt forms such as acetate (water
solubility=45.6 parts per 100 parts). In the case of lead nitrate
(soluble in water at 56 parts per 100 parts), a relatively high
amount of lead was impregnated into the mesoporous carbon, but a
much less efficient result was obtained for the microporous
carbon.
[0318] The data in FIG. 6 depict the DFT pore volume data for
mesoporous activated carbon before (open circles) and after (solid
diamonds) impregnation with lead acetate. DFT parameters for this
lead-impregnated carbon are given in Table 6. It can be seen that
the mesoporous after lead (II) acetate) impregnation had a
dramatically reduced micropore volume (and a relatively unchanged
mesopore volume). The impregnation of lead into the micropores
would be consistent with this observation.
TABLE-US-00007 TABLE 6 Data for Lead-Impregnated Mesoporous Carbon
Total Total DFT pore DFT pore BET pore vol- vol- SSA volume ume
<20 {acute over (.ANG.)} ume >20 {acute over (.ANG.)} Sample
(m.sup.2/g) (cc/g) (cc/g) (cc/g) 16 1751 1.48 0.50 0.78 (Before
lead (II) acetate impregnated) 17 1057 1.11 0.26 0.77 (After lead
(II) acetate impregnated)
Example 17
Impregnation of Pyrolyzed Polymer Gel with Lead
[0319] Pyrolyzed polymer gel (900 mg) prepared according to Example
2 was suspended in saturated lead acetate prepared according to
Example 19. The liquid mixture was then shaken overnight at room
temperature. The liquid mixture was then centrifuged and the
supernatant removed. The carbon pellet was washed three times with
deionized water (5 mL) and dried overnight at 45.degree. C. The
lead content of the carbon samples thus prepared was analyzed by
PIXE. As can be seen in Table 7 below, the microporous pyrolyzed
carbon provided more efficient impregnation of lead, i.e., 13.6%,
whereas mesoporous carbon achieved about 1% lead content.
TABLE-US-00008 TABLE 7 Lead Content of Various Pyrolyzed Polymer
Gel Samples Sample Pyrolyzed Carbon Type Lead Source Lead Content
18 Mesoporous Lead (II) acetate 1.012% 19 Microporous Lead (II)
acetate 13.631%
Example 18
Impregnation of Dried Polymer Gel with Lead
[0320] Dried polymer gel (900 mg) prepared according to Example 1
was suspended in saturated lead acetate prepared according to
Example 19. The liquid mixture was then shaken overnight at room
temperature. The liquid mixture was then centrifuged and the
supernatant removed. The polymer gel pellet was washed three times
with deionized water (5 mL) and dried overnight at 45.degree. C.
The lead content of the polymer gel thus prepared was analyzed by
PIXE.
Example 19
Incorporation of Lead During Polymerization of Polymer Gel
[0321] A resorcinol-formaldehyde gel mixture was prepared. The
solids content was 41%, the resorcinol to catalyst ratio was 5:1,
the catalyst was ammonium acetate, and the acetic acid content was
30%. About 20 mL of polymer solution was obtained (prior to placing
solution at elevated temperature and generating the polymer gel).
To this solution, about 5 mL of saturated lead (II) acetate in 25%
acetic acid solution was added. The resulting final acetic acid
content was thus about 29%, and the resulting final solids content
was about 33%. The solution was then stored at 45.degree. C. for
about 5 h, followed by 24 h at 85.degree. C. to fully induce the
formation of a lead-containing polymer gel. This gel was disrupted
to create particles, and the particles were frozen in liquid
nitrogen and then dried in a lyophilizer as follows. The
liquid-nitrogen frozen material was poured into a tray, and the
tray was placed on a lyophilizer shelf pre-chilled to -30.degree.
C. The chamber pressure was then lowered to and maintained at about
150 to 300 mTorr. The shelf temperature was ramped from -30.degree.
C. to +50.degree. C. over an hour, and then held at 50.degree. C.
for about 8 hours. The dried polymer gel (Sample 20) was found to
contain 7.008% lead by PIXE analysis.
[0322] Lead-containing activated carbon was then produced as
follows. The resulting dried lead-containing polymer gel was
pyrolyzed and activated by heating from room temperature to
850.degree. C. under nitrogen gas at a ramp rate of 20.degree. C.
per min, followed by a hold for 4 hours at 850.degree. C. under
carbon dioxide, followed by cooling under nitrogen from 850.degree.
C. to ambient over several hours.
Example 20
Purity Analysis of Carbon Materials and Polymer Gels Comprising
Lead
[0323] The lead impregnated carbon materials (Samples 8-15, 18 and
19) and lead impregnated polymer gel (Sample 20) were analyzed by
PIXE to determine the lead and other elemental content. These data
are tabulated in Table 8. Elements such as tantalum, chlorine and
aluminum were not typically observed in the non-impregnated carbon
materials or polymer gels, accordingly their presence in the
impregnated samples is attributed to impurities in the lead source.
Higher purity carbon materials and polymer gels can be prepared by
using purified sources of lead.
TABLE-US-00009 TABLE 8 Purity Analysis of Carbon Materials &
Polymer Gels Comprising Electrochemical modifiers Element
Concentration Element S. 8 S. 9 S. 10 S. 11 S. 12 S. 13 S. 14 S. 15
S. 18 S. 19 S. 20 Pb (%) 7.892 6.526 0.294 2.427 1.855 1.169 0.0084
0.0027 1.012 13.631 7.008 Fe (ppm) 7 8 3 ND 7 3 6 2 ND ND 6 Cl
(ppm) 312 254 20 103 85 66 ND ND 41 ND ND Si (ppm) 97 94 27 ND 43
ND 29 ND ND ND ND Ni (ppm) ND ND ND ND ND ND ND ND ND ND 5 Ta (ppm)
64 45 ND 15 18 10 ND ND 7 107 56 Al (ppm) ND 72 ND ND 47 ND 38 ND
ND ND ND Ca (ppm) ND ND 7 ND ND 10 4 9 ND ND ND Co (ppm) ND ND ND
ND ND ND 12 ND ND ND ND S (ppm) ND ND ND ND ND ND 23 23 ND ND ND Cu
(ppm) ND ND ND ND ND ND 2 1 ND ND ND *ND = not detected by PIXE
analysis
Example 21
Preparation of a Mesoporous Carbon Material
[0324] A polymer gel was prepared and pyrolyzed (but not activated)
according to Examples 1 and 2. The carbon material was analyzed and
determined to comprise a specific surface area of about 675
m.sup.2/g, a total pore volume of about 0.70 cc/g and a tap density
of about 0.45 g/cc. The pore size distribution of the mesoporous
carbon material is presented in FIG. 7.
[0325] Electrochemical modifiers are incorporated in the mesoporous
carbon material as described above. For example, electrochemical
modifiers are incorporated during the polymerization stage, into
the dried (or undried polymer gel) or after pyrolysis of the
polymer gel.
Example 22
Preparation of a Dip Coated Carbon Electrode
[0326] A carbon slurry is prepared following Example 10.
Commercially available lead wire is cut to a length of 3 inches.
The wire is dipped into the carbon slurry for 10 seconds and then
allowed to air dry. Further coatings are applied as needed by
successive dipping and drying. Excess solvent is removed by heating
in an oven to at least 65.degree. C. Electrochemical modifiers are
incorporated into the carbons as described above. For example,
electrochemical modifiers are incorporated during the
polymerization stage, into the dried (or undried polymer gel) or
after pyrolysis of the polymer gel. The mass of carbon material on
each lead wire may vary between 5 and 120 mg, as seen in FIG. 8.
The thickness of the dip-coated electrode may also vary between
0.001 and 0.12 cm. The carbon coating volume and the carbon mass
have a direct linear relationship. As the thickness and length of
the coating increases, the amount of carbon on each electrode also
increases.
Example 23
Water Uptake Properties of Carbon
[0327] In certain embodiments, the carbon is measured by the mass
of water that can be absorbed. Carbon coated lead electrodes are
made using Example 25. The electrodes are submerged in deionized
water for 10 minutes and weighed. The mass change before and after
soaking is recorded (see Table 9). There is a clear linear inverse
relationship between the water adsorption and the tap density of
the carbon (correlation of 97%). FIG. 9 depicts the relationship
between the water adsorption and the total pore volume for
activated and non-activated carbons. The more water absorption, the
greater the surface area is exposed to water molecules and the
capability of increasing the available lead-sulfate nucleation
sites at the liquid-solid interface. The water accessible pores
also allow for the transport of electrolyte into the center of the
lead pasted plate for additional material utilization. A surprising
result is that the water adsorption has no relationship to Specific
Surface Area, carbon pH or quantity of impurities.
TABLE-US-00010 TABLE 9 Properties of exemplary carbon samples Water
Total Uptake SSA Pore Tap Water versus PV (m.sup.2/ Vol. Density
Adsorp. (g H.sub.2O/cc Imp.* No. g) (cc/g) (g/cc) D50
(g.sub.H20/g.sub.C) carbon) Act?* pH (ppm) C1 810 0.91 0.22 4.17
2.058 2.2615 No 5.9 62.43 C2 2029 1.04 0.34 7.3 1.3415 1.2899 Yes
7.9 55.06 C3 707 0.566 0.442 6.19 0.947 1.6731 No 5.4 59.238 C4
1823 0.82 0.53 6.9 0.6237 0.7606 Yes 3.8 66.035 C5 388 0.15 0.567
10.82 0.4058 2.7053 No 8.3 N/A C6 1741 1.35 0.22 5.4 2.089 1.5474
Yes 8.4 6.5 Comp 1 1573 0.73 0.413 5.8 0.859 1.1767 Yes 3.647 734
*Act. = Activated, Imp. = PUCE impurities
Example 24
Water Adsorption of Carbon in Varied Humidity
[0328] The initial step of negative plate formation is high and low
exposures to humidity in order to convert available elemental lead
to lead oxide. Depending on the adsorption of water by the carbon
additives, the formation process may change.
[0329] In order to test the uptake of water by the carbon, five
sealed chambers were established, each with a pre-determined
humidity. Approximately 20 mL of saturated solutions of the
following salts were first prepared: potassium sulfate (0.12 g/mL),
sodium chloride (0.37 g/mL), magnesium nitrate (1.25 g/mL),
magnesium chloride (0.56 g/mL), lithium chloride (0.80 g/mL). Each
of these solutions were placed in a separate desiccator to produce
a respective closed system relative humidity as follows: potassium
sulfate=97%, sodium chloride=75%, magnesium nitrate=52%, magnesium
chloride=33%, lithium chloride=11%. One gram portions of each
carbon were placed in a glass vial (weight previously recorded)
then heated in a 105.degree. C. oven for >2 hours to remove any
residual moisture. The carbon samples were weighed after drying and
placed in each desiccator with different respective humidity. After
sitting undisturbed between 30 and 60 days the carbon samples are
removed and re-weighed to determine weight percent gain due to
moisture adsorption.
[0330] In various embodiments, different saturated salt solutions
are used to provide different humidity environments (e.g.,
potassium carbonate=43%, potassium chloride=85%, potassium
nitrate=94%). In other embodiments, larger or smaller quantities of
carbon are used depending on the size and factors associated with
the experiment setup. For instance, large quantities of carbon may
provide less error when determining percent weight gain or loss
from moisture adsorption.
[0331] The percent weight gain measured over a two week span is
presented in FIG. 10.
Example 25
Electrochemical Performance of a Device Comprised of Lead-Carbon
Electrodes
[0332] Lead-carbon pastes were mixed according to the general
procedures described above. The pastes were pasted onto two lead
alloy grids and dried at 85.degree. C. for 24 hours. The pasted
grids were assembled into a two-electrode symmetric prismatic cell
arrangement in an open beaker configuration using AGM woven
fiberglass as the separator material and 4.8 molar sulfuric acid as
the electrolyte. The pasted grid electrodes were kept together
using two Teflon plates fastened together with Teflon screws and
nuts. Prior to electrochemical testing the plates were allowed to
soak in the sulfuric acid electrolyte for 15 minutes. The
capacitance of the cells were measured based on the discharge data
of a galvanostatic charge/discharge profile to 0.9V and 0V at a
symmetric current density ranging from 0.1 A/g carbon to 10 A/g
carbon. A set of conditioning steps may be run prior to capacitance
measurement. The low voltage window limit was chosen to inhibit
pseudocapacitance due to water electrolysis or Faradaic charge
transfer of the lead-acid battery system. Capacitance was
determined from the equation: C=(.DELTA.t*I)/.DELTA.V where the
change in time is recorded between the change in discharge voltage.
The size of electrodes may range according to a desired cell
configuration (e.g., 1 in..times.1 in., 3 in..times.3 in., 5
in..times.5 in., etc).
[0333] A surprising result is that the maximum capacitance occurs
for a carbon with a neutral pH with the smallest D100. There is a
clear relationship between the lead-carbon surface area and the
capacitance. As the surface area increases, the available carbon
sites for energy storage and the capacitance increases.
[0334] A highly unexpected result, however, is that sample B has
the lowest specific surface area compared to other carbon-lead
systems, but has the greatest capacitance. The lead-carbon blend
results can be compared to what is predicted from the carbon
capacitance results. FIG. 11 depicts the relationship between
gravimetric capacitance of carbon with the specific surface area in
acetonitrile electrolyte, while FIG. 12 shows the relationship
between gravimetric capacitance of carbon-lead blends and their
surface area. For sample B, with a surface area of 810, it is
predicted that the carbon will have no measureable capacitance in
either sulfuric acid or in acetonitrile. Table 10 shows the
predicted versus the actual capacitance as measured in F per gram
of carbon. Surprisingly, sample B has the highest capacitance
despite having a predicted value of 0 F/g.
[0335] Capacitance may also be measured by the F per surface area
of the lead-carbon blend (seen in Table 11). Using this metric,
sample B has 3.times. capacitance than sample D and 10.times.
capacitance over sample F.
TABLE-US-00011 TABLE 10 Actual and predicted capacitance of carbon
samples Capacitance (F/g) Sample Acetonitrile/TEATFB Sulfuric
Acid/H.sub.2O A 0 0 B <20 375.99 C <20 11.85 D 104.80 344.34
E 114.02 315.83 F 112.45 296.73
TABLE-US-00012 TABLE 11 Electrochemical properties of carbons and
carbon-lead blends Pb-C Carbon Pb-C Pore Capaci- Capacitance Sam-
SSA SSA Volume tance (F/m2 of ple (m2/g) (m2/g) (cm3/g) (F/g) Pb-C)
pH B 810 2.4394 0.0046 376.0 1.54 5.9 C 705 2.7687 0.0025 11.85
0.075 3.8 D 1741 16.849 0.0130 344.34 0.409 8.4 F 1859 11.5317
0.0036 296.73 0.0116 8.3
Example 26
Preparation of Pasted Grids
[0336] Lead pasted grids are constructed as known in the art. Lead
(II) oxide (PbO) pasted grids were constructed by first mixing the
PbO paste. 40 grams of PbO powder is mechanically mixed with 0.4
grams expander pack from Hammond Expander and 0.4 grams
high-surface area carbon. Once a homogeneous powder mixture was
obtained, 5 milliliters of distilled water was added and the
contents were mixed in a planetary mixer for 1 minute at 2000 rpm.
An additional 4 milliliters of 4.8M sulfuric acid was added to the
contents then mixed in the planetary mixer again for 30 seconds at
2000 rpm. The paste was hot due to the exothermic reaction of the
PbO and sulfuric acid to form lead sulfate. The paste was cooled to
room temperature before measuring paste density and pasting grids.
Paste density was measured using a small plastic container with a
known volume. The paste was added to the container until completely
filled and flush with the top then weighed to determine density.
The paste was applied to lead alloy grids by hand using a rubber
spatula. The pasted grids were dried in a convection oven at
85.degree. C. for 24 hours, at which point, they were ready for
testing.
[0337] Different oxides of lead may be pasted other than PbO. In
another embodiment the PbO powder is replaced with Pb metal powder
or lead (KIM oxide (Pb.sub.3O.sub.4).
[0338] The liquid may be added in different orders than previously
explained. In a further embodiment the water and acid are first
pre-mixed to create a lower molarity solution (e.g. 1M) before
being added in a single step to the paste. In still another
embodiment only water is added to the paste. After the grids are
pasted, they are submerged in 4.8M sulfuric acid for a specific
period of time (e.g. 10 seconds, 1 minute, 1 hour, etc.) to form
the lead sulfate.
[0339] In another embodiment the pasted grids are dried at lower
temperatures (e.g. 40, 50, 60.degree. C.) or higher temperatures
(e.g. 90, 100, 120.degree. C.) for longer or shorter periods of
time (e.g. 0, 2, 4, 6, 8, 10, 12, 36, 48 hours).
Example 27
Incorporation of Carbon into Pasted Grids
[0340] Carbon can be incorporated into lead pasted plates using
methods known in the art. 40 grams of PbO powder is added to a
plastic container followed by 0.4 grams of expander pack and 0.4
grams of high-surface area carbon. The mixture is stirred with a
spatula by hand to mix the dry powders. Then 5 milliliters of water
is added to the powders and the content are mixed in a planetary
mixer for 1 minute at 2000 rpm. At this time, an additional 4
milliliters of 4.8M sulfuric acid is added then the contents are
mixed again for 30 seconds at 2000 rpm. At this point a homogeneous
yellow paste is obtained with the carbon fully incorporated.
[0341] In some embodiments, the high-surface area carbon is wetted
with water or formed into a slurry prior to adding to the PbO
powder/expander mixture. In other embodiments, more or less solvent
(water/acid) is used to bring the paste to a desired/tailored
density (e.g. 5 mL acid/4 mL water, 2 mL acid/4 mL water, etc.). In
still other embodiments, the content of high-surface area carbon is
either increased or decreased from that in Example 1 (e.g. 0.5 wt
%, 2 wt %, 3 wt %, etc.)
[0342] Tables 12 and 13 show the physical properties of the pastes
(i.e., carbon-lead blends). The density of the pastes with lead are
greater than with lead oxide. Each carbon was made with both lead
and lead oxide powder. Using lead powder, sample B had one of the
greatest paste densities (.about.6.2 g/cc) while the paste density
of sample J when mixed with lead oxide was the lowest (.about.3.8
g/cc). FIG. 13 shows the relationship of paste density to
solvent:solid ratio.
[0343] The paste ratio as known in the lead-acid battery art,
should be approximately 4 g/cc. Someone who is familiar in the art
would be able to modify the water and carbon content from the table
below in order to achieve the optimal paste density.
TABLE-US-00013 TABLE 12 Properties of Exemplary Carbon-Lead Blends
Paste Pb Mass Lead Density Carbon mass Expander H.sub.2O
H.sub.2SO.sub.4 H.sub.2SO.sub.4 Liquid Mass Solvent: % No. Type
(g/cc) mass (g) (g) mass (g) (g) (mL) (g) (g) Solid (g) Solid
carbon A Pb 6.156 0 37.8 0.378 2.1 2.1 2.688 4.788 38.178 0.1254 0%
B Pb 6.1875 0.4 40 0.4 2.1 2.1 2.688 4.788 40.8 0.1174 1% C Pb
6.157 2 100 1 5.58 5 6.4 11.98 103 0.1163 2% D Pb 5.697 0.756 37.8
0.378 2 2 2.56 4.56 38.934 0.1171 2% E Pb 5.875 0.4 40 0.4 2.1 2.1
2.688 4.788 40.8 0.1174 1% F Pb 6.25 0.378 37.8 0.378 2 2 2.56 4.56
38.556 0.1183 1% G Pb 6.125 0.4 40 0.4 2.1 2.1 2.688 4.788 40.8
0.1174 1% H Pb 6.125 0.4 40 0.4 2.1 2.1 2.688 4.788 40.8 0.1174 1%
I PbO 4.258 0 37.8 0.378 5 4 5.12 10.12 38.178 0.2651 0% J PbO 3.75
0.378 37.8 0.378 5 4 5.12 10.12 38.556 0.2625 1% K PbO 4.125 0.378
37.8 0.378 5 4 5.12 10.12 38.556 0.2625 1% L PbO 4 0.378 37.8 0.378
5 4 5.12 10.12 38.556 0.2625 1% M PbO 4.2 0.378 37.8 0.378 5 4 5.12
10.12 38.556 0.2625 1% N PbO 4.156 0.378 37.8 0.378 5 4 5.12 10.12
38.556 0.2625 1% O PbO 4.0938 0.378 37.8 0.378 5 4 5.12 10.12
38.556 0.2625 1%
TABLE-US-00014 TABLE 13 Properties of Exemplary Carbon-Lead Blends
C particle Pb-C Total Carb. vol: Pb Total Carbon Pb-C Pore mass
mass Carbon Pb vol Particle Expander vol Carbon SSA SSA Volume
Particle Size No. (g) % vol (cc) (cc) Vol vol (cc) (cc) vol %
(m2/g) (m2/g) (cm3/g) D10 D50 D100 A 38.18 0.00 0.00 5.37 0.00 0.56
5.94 0.00 N/A -0.0785 0.0022 0.392 1.85 16.3 B 40.80 0.98 1.82 5.69
0.32 0.60 8.10 22.45 810 2.4394 0.0046 0.309 1.83 11.2 C 103.00
1.94 4.55 14.21 0.32 1.49 20.25 22.45 705 2.7687 0.0025 0.43 4.85
27.4 D 38.93 1.94 3.44 5.37 0.64 0.56 9.37 36.66 1741 16.849 0.0130
0.563 4.12 14.4 E 40.80 0.98 0.91 5.69 0.16 0.60 7.19 12.64 1888
8.9912 0.0059 0.409 3.2 23.5 F 38.56 0.98 0.86 5.37 0.16 0.56 6.80
12.64 1859 11.5317 0.0036 N/A N/A N/A G 40.80 0.98 0.97 5.69 0.17
0.60 7.25 13.36 1699 39.4625 0.0180 0.331 2.46 16.4 H 40.80 0.98
2.06 5.69 0.36 0.60 8.34 24.66 20 0.0537 0.0003 0.431 3.38 18.6 I
38.18 0.00 0.00 9.48 0.00 0.56 10.04 0.00 N/A 0.7183 0.0048 0.427
2.96 12.7 J 38.56 0.98 1.72 9.48 0.18 0.56 11.76 14.61 810 1.7482
0.0058 0.63 2.71 14.4 K 38.56 0.98 1.72 9.48 0.18 0.56 11.76 14.61
1741 4.3645 0.0084 0.552 5.51 27.4 L 38.56 0.98 1.22 9.48 0.13 0.56
11.26 10.81 1888 5.2225 0.0066 0.564 4.26 13.4 M 38.56 0.98 0.86
9.48 0.09 0.56 10.90 7.88 1859 2.6179 0.0017 0.937 6.12 24 N 38.56
0.98 0.92 9.48 0.10 0.56 10.95 8.35 1699 1.6655 0.0013 0.43 2.75
12.7 O 38.56 0.98 1.94 9.48 0.21 0.56 11.98 16.22 20 0.0049 0.0000
0.342 2.94 18.6
Example 28
Wettability of Carbon for Paste Preparation
[0344] The amount of additional water needed to properly paste lead
grids as negative active material (NAM) depends upon the physical
properties of the carbon, such as pore volume and pore type. The
point at which the carbon is fully wet is determined through
titration of water into carbon and mechanical mixing. Wettability
of the carbon is determined as follows: 2.409 grams of meso-porous
carbon from Example 25 is combined with water in a planetary mixer.
An R-Factor can be used to assess the amount of water needed to
fully wet a carbon. At 4 mL (R=1.6603 mL water/g carbon), the
mixture visibly transitions from partially wet to fully wet. FIG.
14 depicts the water needed to fully wet the carbon and the pore
volume of the carbon, and FIG. 15 shows the pore volume
distribution for the tested carbons. In one embodiment the carbon
has high pore volume where the R-value >1.6 mL/g. In another
embodiment the carbon has a medium pore volume where the R-value is
between 1.2 and 1.6 mL/g. In yet another embodiment the carbon has
a low pore volume where the R-value is less than 1.2 mL/g. The more
electrolyte access to the interior of the structure the more active
material utilization. In some embodiments, the highest pore volume
carbon allows for the greatest access of electrolyte to the
internal lead structure.
Example 29
Acid Titration Properties of Carbon
[0345] 0.25 grams of carbon are measured into a 60 mL polypropylene
bottle. 45% of 37% sulfuric acid aqueous solution is added to the
bottle and sealed. The bottle is secured and agitated for 24 hours.
The liquid is then filtered from the solids and titrated using
NaOH, as known in the art. Plotted in FIG. 16 is the change in the
molarity of sulfuric acid solution versus the pH of activated and
pre-actived carbon. A positive change in molarity per carbon
indicates that the solution was more acidic after the test. A
negative change in molarity per carbon indicates that the solution
was more basic after the test.
[0346] An unexpected result was the effect of heat treatment on
activated carbons. Once activated carbons are heat treated to a
pH>7, the change in molarity per gram carbon becomes independent
of the carbon pH. It is only for non-heat treated carbon that there
is a direct correlation between the change in molarity per carbon
and the pH. There is an unexpected maxiuma in the change in
molarity of the solution per carbon when carbon is close to a
neutral pH (between 5 and 7). This is for both activated and
pre-actived carbons. In other embodiments the change in molarity
per carbon is negative, indicating more basic from a control, as
seen from carbons with low (<5). In yet other embodiments the
acid adsorption as measured as a change in molarity per carbon is
not dependent upon the pH for pH values above 7.
[0347] Yet another surprising result was that the change in
molarity of the solution per carbon had no dependence upon the pore
volume or pore type (micro versus mesoporous). In fact, the only
correlation is between the pH and the change in molarity. In an
even more surprising result, the more acid carbon did not yield
more acid solution, rather the solution was actually more basic
than the control. As previously explained, this unexpected result
gives rise to the local maxima for a semi-neutral carbon pH.
Example 30
Alternative Preparation of a Carbon Material
[0348] A carbon material was prepared according to the procedures
described in PCT App. No. US/2011/067278, which application is
hereby incorporated by reference in its entirety. Briefly, polymer
gel was prepared by polymerization of resorcinol and formaldehyde
(0.5:1) in a water/acetic acid solvent (80:20) in the presence of
ammonium acetate catalyst. The resultant polymer to solvent ratio
was 0.3, and the resorcinol to catalyst ratio (R/C) was 25. The
reaction mixture was placed at elevated temperature (incubation at
45.degree. C. for about 6 h followed by incubation at 85.degree. C.
for about 24 h) to allow for gellation to create a polymer gel.
Polymer gel particles were created from the polymer gel with a rock
crusher through a screen with 3/4 inch sized holes. The particles
were flash frozen by immersion in liquid nitrogen, loaded into a
lyophilization tray at a loading of 3 to 7 g/in.sup.2, and
lyophilized at approximately 50 to 150 mTorr. The time to dry (as
inferred from time for product to reach within 2.degree. C. of
shelf temperature) varied with product loading on the lyophilizer
shelf.
[0349] The mass loss on drying the polymer gel was approximately
72%. The surface area of the dried polymer gel was determined to be
691 m.sup.2/g, the total pore volume was 1.05 cc/g and the tap
density was 0.32 g/cc. Dried polymer gel materials comprising
different properties (e.g., surface area, pore structure, etc.) can
be prepared by altering the drying conditions (e.g., pressure,
temperature, time, etc.) described above.
[0350] Dried polymer gel prepared according was pyrolyzed by
passage into a rotary kiln at 900.degree. C. with a nitrogen gas
flow of 200 L/h. The surface area of the pyrolyzed dried polymer
gel was examined by nitrogen surface analysis using a surface area
and porosity analyzer. The measured specific surface area using the
standard BET approach was 737 m.sup.2/g, the total pore volume was
0.64 cc/g. Carbon materials comprising different properties (e.g.,
surface area, pore structure, etc.) can be prepared by altering the
pyrolysis conditions (e.g., temperature, time, etc.) described
above.
[0351] From the DFT cumulative volume plot for the activated carbon
material, it was determined that about 40% of the pore volume
resides in micropores and about 60% of the pore volume resides in
mesopores. Carbon materials comprising different properties (e.g.,
surface area, pore structure, etc.) can be prepared by altering the
activation conditions (e.g., temperature, time, etc.) described
above.
[0352] Pyrolyzed carbon prepared was jet milled using a
manufacturing scale 15 inch diameter jet mill. The average particle
size after jet milling was about 4 to 7 microns. Properties of the
carbon material are summarized in Table 14. Table 15 summarizes the
range of properties of various carbon embodiments prepared
according the above procedures.
TABLE-US-00015 TABLE 14 Physiochemical Properties of Carbon
Material Test Parameter Result Tap Density Tap Density (g/cc) 0.43
N2 Sorption Isotherm Specific Surface Area (m.sup.2/g) 737 Total
pore volume (cc/g) 0.64 DFT Pore volume >20 .ANG. (cc/g) 0.38
N.sub.2 (p/p0).sub.95/(p/po).sub.5: 2.0-2.7 2.2 (i.e., "P95/P5")
Thermal Gravimetric % weight loss observed between 1.0 Analysis
(TGA) 250 to 850 C. Ash Content Calculated from PIXE elemental
0.0008 data (%) PIXE Purity Sulfur (ppm): ND Silicon (ppm): ND
Calcium (ppm): ND Iron (ppm): 6.2 Nickel ppm): 1.1 Zinc (ppm): ND
Copper (ppm): ND Chromium (ppm): ND All other elements: ND ND = not
detected
Example 31
Alternative Preparation of a Carbon Material
[0353] A carbon material having increased energy density with
balanced power performance was prepared according to the following
description. A polymer gel was prepared by polymerization of
resorcinol and formaldehyde (0.5:1) in a water/acetic acid solvent
(80:20) in the presence of ammonium acetate catalyst. The resultant
polymer to solvent ratio was 0.3, and the resorcinol to catalyst
ratio (R/C) was 25. The reaction mixture was placed at elevated
temperature (incubation at 45.degree. C. for about 6 h followed by
incubation at 85.degree. C. for about 24 h) to allow for gellation
to create a polymer gel. Polymer gel particles were created from
the polymer gel with a rock crusher through a screen with 3/4 inch
sized holes. The particles were loaded into a lyophilization tray
at a loading of 3 to 7 g/in.sup.2, frozen on the shelf of a
freeze-dryer until particles were frozen below -30.degree. C. The
frozen particles were lyophilized at approximately 50 mTorr. The
time to dry (as inferred from time for product to reach within
2.degree. C. of shelf temperature) varied with product loading on
the lyophilizer shelf. At manufacturing scale, polymer gel
particles were loaded on lyophilization trays in a -30.degree. C.
cold room and frozen over the course of 24 hours. These frozen
particles were lyophilized at approximately 120 mTorr. The time to
dry (as inferred from time for product to reach within 2.degree. C.
of shelf temperature) varied with product loading on the
lyophilizer shelf.
[0354] The mass loss on drying the polymer gel was 74.1%. The
surface area of the dried polymer gel was determined to be 515
m.sup.2/g, the total pore volume was 0.39 cc/g and the tap density
was 0.22 g/cc.
[0355] Dried polymer gel prepared according to the above procedure
was pyrolyzed by passage into a furnace at 625.degree. C. with a
nitrogen gas flow of 400 L/h. At manufacturing scale, dried polymer
gel prepared according to the above procedure was pyrolyzed by
passage into a rotating kiln furnace set with three hot zones of
685.degree. C., 750.degree. C., and 850.degree. C.
[0356] The surface area of the pyrolyzed dried polymer gel
pyrolyzed by passage into a furnace at 625.degree. C. was examined
by nitrogen surface analysis using a surface area and porosity
analyzer. The measured specific surface area using the standard BET
approach was 622 m.sup.2/g, the total pore volume was 0.33 cc/g.
The surface area of the pyrolyzed dried polymer gel pyrolyzed by
passage into a rotary kiln furnace set with three hot zones of
685.degree. C., 750.degree. C., and 850.degree. C. was examined by
nitrogen surface analysis using a surface area and porosity
analyzer. The measured specific surface area using the standard BET
approach was 588 m.sup.2/g, the total pore volume was 0.25 cc/g.
Carbon materials comprising different properties (e.g., surface
area, pore structure, etc.) can be prepared by altering the
pyrolysis conditions (e.g., temperature, time, etc.) described
above.
[0357] Pyrolyzed carbon material prepared according to above was
activated in a batch rotary kiln at 900.degree. C. under CO.sub.2
for approximately 840 min, resulting in a total weight loss of 50%.
In another case, Pyrolyzed carbon material prepared according to
above was activated in a fluidized bed reactor at 925.degree. C.
under CO.sub.2.
[0358] The surface area of the activated carbon produced by a batch
rotary kiln as described above was examined by nitrogen surface
analysis using a surface area and porosity analyzer. The measured
specific surface area using the BET approach was 1857 m.sup.2/g,
the total pore volume was 0.87 cc/g and the tap density was 0.41
g/cc. In the second case using a fluidized bed reactor, the
resultant material was also measured by nitrogen adsorption
analysis and the measured specific surface area using the BET
approach was 2046 m.sup.2/g, and the total pore volume was 1.03
cc/g.
[0359] From the DFT cumulative volume plot for the activated carbon
material, it was determined that the 80% of the pore volume resides
in micropores and 20% of the pore volume resides in mesopores. In
other examples, it was determined that 70% of the pore volume
resides in the micropores and 30% of the pore volume resides in the
mesopores. Carbon materials comprising different properties (e.g.,
surface area, pore structure, etc.) can be prepared by altering the
activation conditions (e.g., temperature, time, etc.) described
above.
[0360] Activated carbon prepared was jet milled using a Jet
Pulverizer Micron Master 2 inch diameter jet mill and at the
manufacturing scale, a 15 inch diameter jet mill was used. The
average particle size after jet milling was about 4 to 7
microns.
[0361] Chemical species on the surface of the activated carbon was
removed with a heat treatment process by heating the carbon in an
elevator furnace under nitrogen gas for 1 hour at 900.degree. C.
The pH was measured on the treated carbon and was 7.9 indicating a
lack of oxygen containing surface functional groups. Properties of
various carbons prepared by the above method are summarized in
Table 14.
Example 32
Alternative Preparation of a Carbon Material
[0362] A carbon material having increased energy density with
balanced power performance was prepared according to the following
description. A polymer gel was prepared by polymerization of
resorcinol and formaldehyde (0.5:1) in a water/acetic acid solvent
(80:20) in the presence of ammonium acetate catalyst. The resultant
polymer to solvent ratio was 0.3, and the resorcinol to catalyst
ratio (R/C) was 25. The reaction mixture was placed at elevated
temperature (incubation at 45.degree. C. for about 6 h followed by
incubation at 85.degree. C. for about 24 h) to allow for gellation
to create a polymer gel. Polymer gel particles were created from
the polymer gel with a rock crusher through a screen with 3/4 inch
sized holes.
[0363] Polymer gel particles were prepared was pyrolyzed by passage
into a furnace at 625.degree. C. with a nitrogen gas flow of 400
L/h.
[0364] The surface area of the pyrolyzed dried polymer gel was
examined by nitrogen surface analysis using a surface area and
porosity analyzer. The measured specific surface area using the
standard BET approach was 585 m.sup.2/g, the total pore volume was
0.28 cc/g. Carbon materials comprising different properties (e.g.,
surface area, pore structure, etc.) can be prepared by altering the
pyrolysis conditions (e.g., temperature, time, etc.) described
above.
[0365] Pyrolyzed carbon material prepared according to above was
activated in a 4'' Fluidized Bed Reactor at 900.degree. C. under a
CO.sub.2 for approximately 15 hours.
[0366] The surface area of the activated carbon was examined by
nitrogen surface analysis using a surface area and porosity
analyzer. The measured specific surface area using the BET approach
was 2529 m.sup.2/g, the total pore volume was 1.15 cc/g and the tap
density was 0.36 g/cc.
[0367] From the DFT cumulative volume plot for the activated carbon
material, it was determined that the 68% of the pore volume resides
in micropores and 32% of the pore volume resides in mesopores.
Carbon materials comprising different properties (e.g., surface
area, pore structure, etc.) can be prepared by altering the
activation conditions (e.g., temperature, time, etc.) described
above.
[0368] Activated carbon prepared was jet milled using a Jet
Pulverizer Micron Master 2 inch diameter jet mill. The average
particle size after jet milling was about 4 to 7 microns.
Example 33
Properties of Various Carbon Materials
[0369] Carbon materials having various properties can be prepared
according to the general procedures described above. Table 14
summarizes the properties of carbon materials prepared according to
the noted examples.
TABLE-US-00016 TABLE 14 Physiochemical Characteristics of Carbon
Samples Total Ratio N.sub.2 Pore adsorbed PV meso/ SSA Volume Tap
Density (P/Po)95/ PV total Example (m.sup.2/g) (cc/g) (g/cc)
(P/Po)5 (%) Purity Ex. 33 600-800 0.5-0.9 0.35-0.45 2.0-3.0 40-60%
<200 ppm impurities Ash: 0.001-0.03% Ex. 1-3 1550-2100 1.2-1.6
0.25-0.35 1.8-2.5 52-60% <200 ppm impurities Ash: 0.001-0.03%
Ex. 1-3 2100-2800 1.5-2.7 0.19-0.28 2.0-2.5 52-60% <200 ppm
impurities Ash: 0.001-0.03% Ex. 34 1800-2200 0.8-1.2 0.30-0.45
1.2-1.6 20-50% <200 ppm impurities Ash: 0.001-0.03% Ex. 35
1800-2600 0.7-1.3 0.25-0.45 1.2-1.8 20-50% <200 ppm impurities
Ash: 0.001-0.03%
[0370] The various embodiments described above can be combined to
provide further embodiments. All of the U.S. patents, U.S. patent
application publications, U.S. patent applications, foreign
patents, foreign patent applications and non-patent publications
referred to in this specification and/or listed in the Application
Data Sheet, are incorporated herein by reference, in their
entirety. Aspects of the embodiments can be modified, if necessary
to employ concepts of the various patents, applications and
publications to provide yet further embodiments. These and other
changes can be made to the embodiments in light of the
above-detailed description. In general, in the following claims,
the terms used should not be construed to limit the claims to the
specific embodiments disclosed in the specification and the claims,
but should be construed to include all possible embodiments along
with the full scope of equivalents to which such claims are
entitled. Accordingly, the claims are not limited by the
disclosure.
* * * * *