U.S. patent application number 11/939494 was filed with the patent office on 2008-05-01 for dry particle based adhesive electrode and methods of making same.
This patent application is currently assigned to Maxwell Technologies, Inc.. Invention is credited to Porter Mitchell, Xiaomei Xi, Linda Zhong, Bin Zou.
Application Number | 20080102371 11/939494 |
Document ID | / |
Family ID | 38664629 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080102371 |
Kind Code |
A1 |
Mitchell; Porter ; et
al. |
May 1, 2008 |
DRY PARTICLE BASED ADHESIVE ELECTRODE AND METHODS OF MAKING
SAME
Abstract
A dry process based capacitor and method for a self-supporting
dry adhesive electrode film for use therein is disclosed.
Inventors: |
Mitchell; Porter; (San
Diego, CA) ; Xi; Xiaomei; (Carlsbad, CA) ;
Zhong; Linda; (San Diego, CA) ; Zou; Bin;
(Chandler, AZ) |
Correspondence
Address: |
MAXWELL TECHNOLOGIES, INC.
9244 BALBOA AVENUE
SAN DIEGO
CA
92123
US
|
Assignee: |
Maxwell Technologies, Inc.
San Diego
CA
|
Family ID: |
38664629 |
Appl. No.: |
11/939494 |
Filed: |
November 13, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10817314 |
Apr 2, 2004 |
7295423 |
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11939494 |
Nov 13, 2007 |
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60486002 |
Jul 9, 2003 |
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60498346 |
Aug 26, 2003 |
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60486530 |
Jul 10, 2003 |
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60498210 |
Aug 26, 2003 |
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60546093 |
Feb 19, 2004 |
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Current U.S.
Class: |
429/231.8 ;
361/502; 361/523; 429/217; 429/521; 429/522; 429/529; 429/532 |
Current CPC
Class: |
C04B 35/63488 20130101;
H01G 9/155 20130101; C04B 35/52 20130101; C04B 35/522 20130101;
C04B 2235/77 20130101; Y02E 60/13 20130101; H01G 11/38 20130101;
H01G 9/00 20130101; H01G 11/22 20130101; H01G 11/42 20130101; C04B
35/634 20130101 |
Class at
Publication: |
429/231.8 ;
361/502; 361/523; 429/217; 429/040 |
International
Class: |
H01M 4/58 20060101
H01M004/58; H01M 4/62 20060101 H01M004/62; H01M 4/86 20060101
H01M004/86; H01G 9/058 20060101 H01G009/058 |
Claims
1. An energy storage device product, comprising: a self-supporting
film consisting of a dry mix of dry carbon and dry binder
particles.
2. The product of claim 1, wherein at least some of the dry mix is
dry fibrillized.
3. The product of claim 1, wherein the dry mix consists of no
processing additive.
4. An energy storage device product, comprising: one or more
self-supporting dry adhesive film comprising a dry mix of dry
binder and dry carbon particles.
5. The product of claim 4, wherein the self supporting dry adhesive
film is a compacted film.
6. The product of claim 5, wherein the dry adhesive film comprises
a thickness of less than 250 microns.
7. The product of claim 4, wherein the self-supporting dry adhesive
film comprises a length of at least 1 meter.
8. The product of claim 4, wherein the self-supporting dry adhesive
film is coupled directly against a substrate.
9. The product of claim 8, wherein the self-supporting dry adhesive
film comprises no processing additive.
10. The product of claim 8, wherein the substrate comprises a
collector.
11. The product of claim 10, wherein the collector comprises
aluminum.
12. The product of claim 8, wherein the product comprises a
collector, and wherein the dry adhesive film is coupled directly
against a surface of the collector.
13. The product of claim 12, wherein the collector is
untreated.
14. The product of claim 10, wherein the collector comprises two
sides, wherein one self supporting dry adhesive film is calendered
directly against one side of the collector, and wherein a second
self supporting dry adhesive film is calendered directly against a
second side of the collector.
15. The product of claim 14, wherein the collector is treated.
16. The product of claim 14, wherein the collector is formed to
comprise a roll.
17. The product of claim 16, wherein the roll is disposed within a
sealed aluminum housing.
18. The product of claim 17, wherein within the housing is disposed
an electrolyte, and wherein the product comprises a double-layer
capacitor.
19. The product of claim 8, wherein at least some of the dry binder
comprises a fibrillizable fluoropolymer, and wherein the dry carbon
particles comprise activated carbon particles and conductive carbon
particles.
20. The product of claim 8, wherein at least some of the dry binder
comprises a thermoplastic, and wherein the dry carbon particles
comprise conductive carbon particles.
21. A capacitor, the capacitor comprising: a collector; the
collector having two sides; and two electrode film layers, wherein
a first electrode film layer is bonded directly onto a first
surface of the collector, and wherein a second electrode film layer
is bonded directly onto a second surface of the collector.
22. The capacitor of claim 21, wherein the two electrode film
layers consist of no processing additives.
23. The capacitor of claim 22, wherein the two electrode layers
comprise a thermoplastic.
24. The capacitor of claim 21, wherein the film layers comprise
substantially zero residues as determined by a chemical analysis of
the layers before impregnation by an electrolyte.
25. The capacitor of claim 24, wherein the residues comprise
hydrocarbons, high boiling point solvents, antifoaming agents,
surfactants, dispersion aids, water, pyrrolidone, mineral spirits,
ketones, naphtha, acetates, alcohols, glycols, toluene, xylene, and
Isopars.TM..
26. The capacitor of claim 23, wherein the layers are impregnated
with an electrolyte.
27. The capacitor of claim 26, wherein the capacitor comprises a
double-layer capacitor.
28. An energy storage device, comprising: one or more continuous
self supporting intermixed film structure comprising dry carbon
particles and dry binder particles, the film structure comprising
about zero parts per million processing additive.
29. The energy storage device of claim 28, wherein the additive is
selected from the group consisting of hydrocarbons, high boiling
point solvents, antifoaming agents, surfactants, dispersion aids,
water, pyrrolidone, mineral spirits, ketones, naphtha, acetates,
alcohols, glycols, toluene, xylene, and Isopars.TM..
30. The energy storage device of claim 28, wherein the film
structure comprises a dry adhesive binder.
31. The energy storage device of claim 28, wherein the film
structure comprises a dry conductive carbon.
32. The energy storage device of claim 28, wherein the film
structure comprises dry activated carbon, dry conductive carbon,
and dry adhesive binder.
33. The energy storage device of claim 28, wherein the film
structure is coupled to a collector.
34. The energy storage device of claim 28, wherein the intermixed
film structure comprises two intermixed film structures coupled to
a collector, wherein a first of the film structures is coupled to a
first side of the collector, and wherein a second of the film
structures is coupled to a second side of the collector.
35. The energy storage device of claim 28, wherein the intermixed
film structure is an electrode film.
36. The energy storage device of claim 35, wherein the electrode
film is an energy storage device electrode film.
37. The energy storage device of claim 36, wherein the electrode
film comprises a capacitor electrode film.
38. A capacitor structure, comprising a collector; and a plurality
of dry processed particles coupled to the collector, wherein the
particles define a long integral dry electrode film.
39. The structure of claim 38, wherein the film comprises dry
conductive carbon and dry adhesive materials.
40. The structure of claim 38, wherein the film comprises one or
more blend of dry particles.
41. The structure of claim 40, wherein a first of the particles
comprises activated carbon, conductive carbon, and a fibrillizable
binder; and wherein a second of the particles comprises conductive
carbon and adhesive binder.
42. An energy storage device electrode, the electrode comprising:
adhesive binder particles; and carbon particles, the carbon
particles comprising a surface, wherein a plurality of the carbon
particles are coupled to each other by the adhesive binder
particles, and wherein a plurality of the carbon particles make
direct carbon particle to carbon particle contact.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention is a continuation of U.S. application
Ser. No. 10/817,314, filed Apr. 2, 2004, entitled "Dry Particle
Based Adhesive Electrode and Methods of Making Same," which claims
priority from commonly assigned Provisional Application No.
60/486,002, filed Jul. 9, 2003; commonly assigned Provisional
Application No. 60/498,346, filed Aug. 26, 2003; commonly assigned
Provisional Application No. 60/486,530, filed Jul. 10, 2003;
commonly assigned Provisional Application No. 60/498,210, filed
Aug. 26, 2003; and commonly assigned Provisional Application No.
60/546,093, filed Feb. 19, 2004. Each of these nonprovisional and
provisional applications is incorporated herein by reference in
their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
energy storage devices that are used to power modern technology.
More particularly, the present invention relates to structures and
methods for making dry particle based adhesive electrode films for
capacitor products.
BACKGROUND INFORMATION
[0003] Devices that are used to power modern technology are
numerous. Inclusive of such devices are capacitors, batteries, and
fuel cells. With each type of device are associated positive and
negative characteristics. Based on these characteristics decisions
are made as to which device is more suitable for use in a
particular application. Overall cost of a device is an important
characteristic that can make or break a decision as to whether a
particular type of device is used. Double-layer capacitors, also
referred to as ultracapacitors and super-capacitors, are energy
storage devices that are able to store more energy per unit weight
and unit volume than capacitors made with traditional
technology.
[0004] Double-layer capacitors store electrostatic energy in a
polarized electrode/electrolyte interface layer. Double-layer
capacitors include two electrodes, which are separated from contact
by a porous separator. The separator prevents an electronic (as
opposed to an ionic) current from shorting the two electrodes. Both
the electrodes and the porous separator are immersed in an
electrolyte, which allows flow of the ionic current between the
electrodes and through the separator. At the electrode/electrolyte
interface, a first layer of solvent dipole and a second layer of
charged species is formed (hence, the name "double-layer"
capacitor).
[0005] Although, double-layer capacitors can theoretically be
operated at voltages as high as 4.0 volts and possibly higher,
current double-layer capacitor manufacturing technologies limit
nominal operating voltages of double-layer capacitors to about 2.5
to 2.7 volts. Higher operating voltages are possible, but at such
voltages undesirable destructive breakdown begins to occur, which
in part may be due to interactions with impurities and residues
that can be introduced into or attach themselves to electrodes
during manufacture. For example, undesirable destructive breakdown
of double-layer capacitors is seen to appear at voltages between
about 2.7 to 3.0 volts.
[0006] Known capacitor electrode fabrication techniques utilize
processing additive based coating and/or extrusion processes. Both
processes utilize binders, which typically comprise polymers or
resins that provide cohesion between structures used to make the
capacitor. Known double-layer capacitors utilize electrode film and
adhesive/binder layer formulations that have in common the use of
one or more added processing additive (also referred throughout as
"additive"), variations of which are known to those skilled in the
arts as solvents, lubricants, liquids, plasticizers, and the like.
When such additives are utilized in the manufacture of a capacitor
product, the operating lifetime, as well maximum operating voltage,
of a final capacitor product may become reduced, typically because
of undesirable chemical interactions that can occur between
residues of the additive(s) and a subsequently used capacitor
electrolyte.
[0007] In a coating process, an additive (typically organic,
aqueous, or blends of aqueous and organic solvents) is used to
dissolve binders within a resulting wet slurry. The wet slurry is
coated onto a collector through a doctor blade or a slot die. The
slurry is subsequently dried to remove the solvent. With prior art
coating based processes, as layer thickness decreases, it becomes
increasingly more difficult to achieve an even homogeneous layer,
for example, wherein a uniform 5 micron thick coating of an
adhesive/binder layer is desired. The process of coating also
entails high-cost and complicated processes. Furthermore, coating
processes require large capital investments, as well as high
quality control to achieve a desired thickness, uniformity, top to
bottom registration, and the like.
[0008] In the prior art, a first wet slurry layer is coated onto a
current collector to provide the current collector with
adhesive/binder layer functionality. A second slurry layer, with
properties that provide functionality of a conductive electrode
layer, may be coated onto the first coated layer. In another prior
art example, an extruded layer can be applied to the first coated
layer to provide conductive electrode layer functionality.
[0009] In the prior art process of forming an extruded conductive
electrode layer, binder and carbon particles are blended together
with one or more additive. The resulting material has dough-like
properties that allow the material to be introduced into an
extruder apparatus. The extruder apparatus fibrillates the binder
and provides an extruded film, which is subsequently dried to
remove most, but as discussed below, typically not all of the
additive(s). When fibrillated, the binder acts as a matrix to
support the carbon particles. The extruded film may be calendared
many times to produce a electrode film of desired thickness and
density.
[0010] Known methods for attaching additive/solvent based extruded
electrode films and/or coated slurries to a current collector
include the aforementioned precoating of a slurry of
adhesive/binder. Pre-coated slurry layers of adhesive/binder are
used in the capacitor prior arts to promote electrical and physical
contact with current collectors, and the current collectors
themselves provide a physical electrical contact point.
[0011] Impurities can be introduced or attach themselves during the
aforementioned coating and/or extrusion processes, as well as
during prior and subsequent steps. Just as with additives, the
residues of impurities can reduce a capacitor's operating lifetime
and maximum operating voltage. In order to reduce the amount of
additive and impurity in a final capacitor product, one or more of
the various prior art capacitor structures described above are
processed through a dryer. Drying processes introduce many
manufacturing steps, as well as additional processing apparatus. In
the prior art, the need to provide adequate throughput requires
that the drying time be limited to on the order of hours, or less.
However, with such short drying times, sufficient removal of
additive and impurity is difficult to achieve. Even with a long
drying time (on the order of days) the amounts of remaining
additive and impurity is still measurable, especially if the
additives or impurities have a high heat of absorption. Long dwell
times limit production throughput and increase production and
process equipment costs. Residues of the additives and impurities
remain in commercially available capacitor products and can be
measured to be on the order of many parts-per-million.
[0012] Binder particles used in prior art additive based
fibrillization steps include polymers and polymer-like substances.
Polymers and similar ultra-high molecular weight substances capable
of fibrillization are commonly referred to as "fibrillizable
binders" or "fibril-forming binders." Fibril-forming binders find
use with powder like materials. In one prior art process,
fibrillizable binder and powder materials are mixed with solvent,
lubricant, or the like, and the resulting wet mixture is subjected
to high-shear forces to fibrillize the binder particles.
Fibrillization of the binder particles produces fibrils that
eventually form a matrix or lattice for supporting a resulting
composition of matter. In the prior art, the high shear forces can
be provided by subjecting the wet mixture comprising the binder to
an extrusion process.
[0013] In the prior art, the resulting additive based extruded
product can be subsequently processed in a high-pressure compactor,
dried to remove the additive, shaped into a needed form, and
otherwise processed to obtain an end-product for a needed
application. For purposes of handling, processing, and durability,
desirable properties of the end product typically depend on the
consistency and homogeneity of the composition of matter from which
the product is made, with good consistency and homogeneity being
important requirements. Such desirable properties depend on the
degree of fibrillization of the polymer. Tensile strength, for
example, commonly depends on both the degree of fibrillization of
the fibrillizable binder, and the consistency of the fibril lattice
formed by the binder within the material. When used as an electrode
film, internal resistance of an end product is also important.
Internal resistance may depend on bulk resistivity--volume
resistivity on large scale--of the material from which the
electrode film is fabricated. Bulk resistivity of the material is a
function of the material's homogeneity; the better the dispersal of
the conductive carbon particles or other conductive filler within
the material, the lower the resistivity of the material. When
electrode films are used in capacitors, such as electro-chemical
double-layer capacitors, capacitance per unit volume is yet another
important characteristic for consideration. In double layer
capacitors, capacitance increases with the specific surface area of
the electrode film used to make a capacitor electrode. Specific
surface area is defined as the ratio of (1) the surface area of
electrode film exposed to an electrolytic solution when the
electrode material is immersed in the solution, and (2) the volume
of the electrode film. An electrode film's specific surface area
and capacitance per unit volume are believed to improve with
improvement in consistency and homogeneity.
[0014] A need thus exists for new methods of producing inexpensive
and reliable capacitor electrode materials with one or more of the
following qualities: improved consistency and homogeneity of
distribution of binder and active particles on microscopic and
macroscopic scales; improved tensile strength of electrode film
produced from the materials; decreased resistivity; and increased
specific surface area. Yet another need exists for capacitor
electrodes fabricated from materials with these qualities. A
further need is to provide capacitors and capacitor electrodes
without the use of processing additives.
SUMMARY
[0015] The present invention provides a high yield method for
making inexpensive, durable, and highly reliable dry electrode
films and associated structures for use in energy storage devices.
The present invention eliminates or substantially reduces use of
additives and eliminates or substantially reduces impurities, and
associated drying steps and apparatus.
[0016] In one embodiment, a process for manufacturing a dry
adhesive film for use in an energy storage device product comprises
the steps of supplying dry carbon particles; supplying dry binder;
dry mixing the dry carbon particles and dry binder; and dry
fibrillizing at least some of the dry binder to create a matrix
within which to support the dry carbon particles as a dry material.
The step of dry fibrillizing may comprise application of
sufficiently high-shear. The high-shear may be applied in a
jet-mill. The application of sufficiently high-shear may be
effectuated by application of a high pressure. The high pressure
may be applied as a high-pressure gas. The gas may comprise oxygen.
The pressure may be greater than or equal to 60 PSI. The process of
claim 6, wherein the gas is applied at a dew point that does not
exceed -40 degrees F. 12 ppm. The process may comprise a step of
compacting the dry material. The step of compacting may be
performed after one pass through a compacting apparatus. The
compacting apparatus may be a roll-mill. After one pass through the
compacting apparatus the dry material may comprise a
self-supporting dry adhesive electrode film. The self-supporting
dry adhesive electrode film may comprise a thickness of about 80 to
250 microns. The self-supporting dry adhesive electrode film may be
formed as a continuous sheet. The sheet may be at least 1 meter
long. The dry material may be manufactured without the use of any
processing additives. The electrode film may be calendered onto a
substrate. The substrate may comprise a collector. The collector
may comprise an aluminum foil. The electrode film may be calendered
directly onto the substrate without use of an intermediate layer.
The dry material may be calendered onto a coated substrate. At
least some of the dry binder may comprise a fibrillizable
fluoropolymer. The carbon particles may comprise activated carbon
and conductive carbon. The dry material may consist of the dry
carbon particles and the dry binder. The dry material may comprise
between about 50% to 99% activated carbon. The dry material may
comprise between about 0% to 25% conductive carbon. The dry
material may comprise between about 0.5% to 20% fluoropolymer
particles. The dry material may comprise between about 80% to 95%
activated carbon and between about 0% to 15% conductive carbon, and
the dry binder may comprise between about 3% to 15% fluoropolymer.
In one embodiment, a method of manufacturing an adhesive electrode
film comprises the steps of mixing dry carbon and dry binder
particles; and forming a self-supporting adhesive film from the dry
particles without the substantial use of any processing additives
such as hydrocarbons, high boiling point solvents, antifoaming
agents, surfactants, dispersion aids, water, pyrrolidone, mineral
spirits, ketones, naphtha, acetates, alcohols, glycols, toluene,
xylene, and Isopars.TM..
[0017] In one embodiment, an energy storage device product may
comprise a self-supporting film consisting of a dry mix of dry
carbon and dry binder particles. At least some of the dry mix may
be dry fibrillized. The dry mix may consist of no processing
additive.
[0018] In one embodiment, an energy storage device product, may
comprise one or more self-supporting dry adhesive film comprising a
dry mix of dry binder and dry carbon particles. The self-supporting
dry adhesive film may be a compacted film. The dry adhesive film
may comprise a thickness of about 100 to about 250 microns. The
self-supporting dry adhesive film may comprise a length of at least
1 meter. The self-supporting dry adhesive film may be coupled
directly against a substrate. The self-supporting dry adhesive film
may comprise no processing additive. The substrate may comprise a
collector. The collector may comprise aluminum. The product may
comprise a collector, and wherein the dry adhesive film is coupled
directly against a surface of the collector. The collector may be
untreated. The collector may comprise two sides, wherein one
self-supporting dry adhesive film is calendered directly against
one side of the collector, and wherein a second self-supporting dry
adhesive film is calendered directly against a second side of the
collector. The collector may be treated. The collector may be
formed to comprise a roll. The roll may be disposed within a sealed
aluminum housing. The housing may be disposed in an electrolyte,
wherein the product comprises a double-layer capacitor. At least
some of the dry binder may comprise a fibrillizable fluoropolymer,
wherein the dry carbon particles comprise activated carbon
particles and conductive carbon particles. At least some of the dry
binder may comprise a thermoplastic, wherein the dry carbon
particles comprise conductive carbon particles.
[0019] In one embodiment, an energy storage product may consist of
a dry fibrillized mix of dry binder and dry carbon particles formed
into a continuous self-supporting adhesive electrode film without
the use of any processing additives. The processing additives not
used may include of hydrocarbons, high boiling point solvents,
antifoaming agents, surfactants, dispersion aids, water,
pyrrolidone, mineral spirits, ketones, naphtha, acetates, alcohols,
glycols, toluene, xylene, and Isopars.TM.. At least some of the dry
binder may comprise a fibrillized dry binder. The binder may be
fibrillized by a high-pressure gas. The high-pressure may comprise
a pressure of more than 60 PSI. The gas may comprise a dew point of
no more than -40 degrees F. 12 PPM.
[0020] In one embodiment, a process for making an energy storage
device comprises the steps of mixing dry carbon particles and dry
binder to form one or more dry mixture; and compacting the one or
more dry mixture to form one or more dry film. The process may
comprise the step of bonding the one or more dry film to a current
collector. The process may comprise the step of bonding the one or
more dry film to a separator. The step of compacting may comprise
heating the carbon particles and binder. The step of compacting may
comprise forming the dry film after one pass through a compacting
device. The dry film may be formed as a long continuous film. The
dry film may be self-supporting. The process of claim 58, further
comprising a step wherein the dry film is bonded directly to the
current collector. The mixing step may comprise dry fibrillizing at
least some of the dry mixture. The mixing step may comprise
subjecting at least some of the dry binder to high shear forces.
The high shear forces may be applied by a high-pressure gas. The
gas may comprise oxygen. The pressure may be greater than or equal
to 60 PSI. The gas may be applied at a dew point that does not
exceed -40 degrees F. 12 ppm. At least some of the dry binder may
comprise thermoplastic particles. The dry binder may include
polyethylene, polypropylene, polyolefin, and non-fibrillizable
fluoropolymer particles. At least some of the dry binder may
comprise fibrillizable fluoropolymer particles. The fibrillizable
fluoropolymer particles may comprise PTFE. At least some of the dry
carbon particles may comprise conductive graphite. At least some of
the dry carbon particles may comprise a mixture of activated carbon
and conductive carbon. The current collector may comprise a metal.
The current collector may comprise aluminum foil. The one or more
dry film may comprise a dry conductive electrode film. The dry film
may consist of a mix of dry carbon particles and dry binder
particles. The dry carbon particles may comprise dry conductive
carbon particles. The dry carbon particles may comprise dry
activated carbon particles. The dry binder may comprise dry
thermoplastic particles. The dry binder may comprise dry
thermoplastic particles, wherein the step of bonding occurs during
application of heat. After compacting, the dry film may comprise a
density of about 0.50 to 0.70 gm/cm.sup.2. The dry binder may
comprise radiation set particles. The dry binder may comprise
thermoset particles. A first dry mixture of the one or more dry
mixture may comprise activated carbon particles, conductive carbon
particles, and first binder particles; and a second dry mixture of
the one or more dry mixture may comprise conductive carbon
particles and second binder particles. The process may comprise a
feeding step, wherein a first dry mixture of the one or more dry
mixture comprises first dry particles, wherein a second dry mixture
of the one or more dry mixture comprises second dry particles,
wherein during the feeding step the first dry particles are
provided as a first stream of dry particles, wherein during the
feeding step the second dry particles are provided as a second
stream of dry particles, and wherein during the mixing step the
second stream is intermixed within the first stream. The second
stream may comprise a distribution of dry particles sizes, wherein
during the mixing step the second stream is intermixed within the
first stream so as to have a similar distribution of particles
sizes as that in the feeding step. The one or more dry mixture may
comprise a first dry film, wherein a second dry mixture of the one
or more dry mixture comprises dry particles, wherein during the
mixing step the dry particles are provided against the first dry
film as a stream of dry particles. The process may comprise the
step of providing an additive-based film, wherein a first dry
mixture of the one or more dry mixture comprises dry particles,
wherein during the mixing step the dry particles are provided
against the additive-based film as a stream of dry particles. The
energy storage device may comprise an energy storage device
electrode, wherein all process steps do not utilize any processing
additives.
[0021] In one embodiment. a blend of dry particles for use in the
dry manufacture of a self-supporting energy storage device
electrode comprises dry carbon particles; and dry binder particles.
The dry carbon particles may comprise activated carbon and
conductive carbon particles, wherein the electrode is a capacitor
electrode. The dry binder particles may comprise a dry
thermoplastic. The dry binder and dry carbon particles may be
intermixed, wherein the dry thermoplastic is distributed within a
thickness of a surface of the intermix with a decreasing gradient
that is greater at a first thickness than a different second
thickness. In one embodiment, an electrode may comprise a
self-supporting dry film including compacted dry binder and dry
carbon particles. The particles may be dry intermixed so as to be
distributed within the film with a gradually decreasing gradient.
The electrode may comprise a collector, wherein a first side of the
dry film is coupled to the collector. The electrode may comprise a
separator, wherein a second side of the dry film is coupled to the
separator. The dry binder may comprise a heated thermoplastic. The
dry carbon particles may comprise conductive carbon particles. The
dry binder may comprise a dry fluoropolymer. The dry carbon
particles may comprise dry conductive carbon particles and dry
activated carbon particles. The dry film may be subjected to heat
heated dry film. The dry carbon film may comprise a density of
about 0.50 to 0.70 gm/cm.sup.2. The dry intermixed particles may
comprise two mixes, wherein as a percentage of a weight of a first
mix, the first mix comprises between about 80% to 95% activated
carbon, between about 0% to 15% conductive carbon, and between
about 3% to 15% fibrillizable fluoropolymer; and wherein as
percentage of weight of a second mix, the second mix comprises
about 40% to 60% binder, and about 40% to 60% conductive carbon.
The dry carbon film may comprise about 1 to 100 parts of the second
mix for about every 1000 parts of the first mix.
[0022] In one embodiment, a capacitor may comprise a plurality of
dry processed particles, the dry processed particles including
binder and carbon particles. The dry processed particles may be
formed as a self-supporting dry electrode film, wherein at least
some of the dry processed particles are compacted against the dry
electrode film. The capacitor may comprise a current collector,
wherein the dry processed particles are dry bonded to the current
collector, and wherein the current collector comprises aluminum.
The may comprise a separator, wherein the dry processed particles
are dry-bonded to the separator. The separator may comprise paper.
The capacitor may comprise a double-layer electrode rated to
operate at a maximum voltage of 3.0 volts or less. The capacitor
may comprise an additive-based electrode film, wherein the dry
processed particles are compacted against the additive based
electrode film. The dry processed particles may be compacted into a
dry self-supporting electrode film by a single pass compaction
device. The capacitor may comprise a sealed aluminum housing,
wherein the dry processed particles are disposed within the
housing. The capacitor may comprise a sealed aluminum housing,
wherein the current collector is coupled to the housing by a laser
weld. The capacitor may comprise a jellyroll type electrode.
[0023] In one embodiment, a capacitor comprises a collector; the
collector having two sides; and two electrode film layers, wherein
a first electrode film layer is bonded directly onto a first
surface of the collector, and wherein a second electrode film layer
is bonded directly onto a second surface of the collector. The two
electrode film layers may include no processing additives. The two
electrode layers may comprise a thermoplastic. The capacitor may
comprise substantially zero residues as determined by a chemical
analysis of the layers before impregnation by an electrolyte. The
residues may be selected from a group consisting of: hydrocarbons,
high boiling point solvents, antifoaming agents, surfactants,
dispersion aids, water, pyrrolidone, mineral spirits, ketones,
naphtha, acetates, alcohols, glycols, toluene, xylene, and
Isopars.TM. The layers may be impregnated with an electrolyte. The
capacitor may comprise a double-layer capacitor.
[0024] In one embodiment, an apparatus for manufacture of an energy
device electrode may comprise one or more feeder, wherein each
feeder provides dry carbon and binder particles for processing by
the apparatus. The apparatus may comprise at least two rollers,
wherein the at least two rollers are disposed to receive the
particles from the feeders to form a dry film from the particles.
The apparatus may comprise a compactor, wherein the compactor is
disposed to receive the particles to form a dry film from the
particles, and wherein the dry film is self-supporting after one
pass-through the compactor. The dry film may comprise a density of
about 0.50 to 0.70 gm/cm.sup.2. The dry film may be a long
continuous film. The dry film may comprise an intermixed dry film,
wherein some of the dry carbon and dry binder particles are
intermixed within the dry film with a first gradient, wherein some
of the dry carbon and dry binder particles are intermixed within
the dry film with a first gradient, wherein the first gradient of
particles provides electrode functionality, and wherein the second
gradient of particles provides adhesive functionality. The
apparatus may comprise at least two heated rollers, wherein the at
least two rollers are disposed to receive the particles to form a
dry electrode film from the mixture. The apparatus may be disposed
to receive a current collector and to calender the dry electrode
film directly to the current collector.
[0025] In one embodiment, an energy storage device electrode
comprises a dry film, wherein the dry film comprises intermixed dry
carbon and dry binder particles, wherein some of the dry carbon and
dry binder particles are intermixed within the dry film with a
first gradient, wherein some of the dry carbon and dry binder
particles are intermixed within the dry film with an opposing
different second gradient, wherein the first gradient of particles
provides electrode functionality, and wherein the second gradient
of particles provides adhesive functionality.
[0026] In one embodiment, an energy storage device comprises one or
more continuous self supporting intermixed film structure
comprising conductive dry carbon particles and dry binder
particles, the film structure consisting of about zero parts per
million processing additive. The additive is selected from the
group consisting of hydrocarbons, high boiling point solvents,
antifoaming agents, surfactants, dispersion aids, water,
pyrrolidone, mineral spirits, ketones, naphtha, acetates, alcohols,
glycols, toluene, xylene, and Isopars.TM.. The film structure may
comprise a dry adhesive binder. The film structure may comprise a
dry conductive carbon. The film structure may comprise dry
activated carbon, dry conductive carbon, and dry adhesive binder.
The film structure may be coupled to a collector. The intermixed
film structure may comprise two intermixed film structures coupled
to a collector, wherein a first of the film structures is coupled
to a first side of the collector, and wherein a second of the film
structures is coupled to a second side of the collector. The
intermixed film structure may be an electrode film. The electrode
film may be an energy storage device electrode film. The electrode
film may comprise a capacitor electrode film.
[0027] In one embodiment, an energy storage device comprises a
housing; a collector, the collector having an exposed surface; an
electrolyte, the electrolyte disposed within the housing; and an
electrode film, wherein the electrode film is impregnated with the
electrolyte, and wherein the electrode film is coupled directly to
the exposed surface. The electrode film may be substantially
insoluble in the electrolyte. The electrode may comprise a dry
adhesive binder, wherein the binder is substantially insoluble in
the electrolyte. The adhesive binder may comprise a thermoplastic,
wherein the thermoplastic couples the electrode film to the
collector. The electrolyte may comprise an acetonitrile type of
electrolyte. In one embodiment, a solventless method for
manufacture of an energy storage device electrode comprises the
steps of providing dry carbon particles; providing dry binder
particles; forming the dry carbon and dry binder particles into an
adhesive energy storage device electrode without the use of any
solvent.
[0028] In one embodiment, a solventless method for manufacture of
an energy storage device electrode comprises the steps of providing
dry carbon particles; providing dry binder particles; intermixing
the dry carbon and dry binder particles to form an adhesive energy
storage device electrode without the use of any solvent.
[0029] In one embodiment, an energy storage device structure
comprises one or more electrode film, wherein the one or more
electrode film is both conductive and adhesive, and wherein the one
or more electrode film is coupled directly to a current
collector.
[0030] In one embodiment, an energy storage device structure
comprises one or more self-supporting dry process based electrode
film. The film may comprise conductive and adhesive particles. The
adhesive particles may comprise a thermoplastic. The electrode may
be a capacitor electrode.
[0031] In one embodiment, a method of adhering capacitor structures
together comprises the steps of providing a first capacitor
material; providing a first dry mixture of particles; and adhering
the first material to the first mixture. The step of adhering may
comprise a step of compacting the material and the particles
together. The material may comprise a second dry mixture of
particles. The material may comprise a current collector. The step
of compacting may form the material and the particles into a
capacitor electrode. The first material may comprise an
additive-based film. The particles may comprise conductive carbon
and binder. The binder may comprise a thermoplastic material. The
step of adhering may occur during application of heat to the
particles. The electrode may comprise a density of about 0.50 to 70
gm/cm.sup.2. The binder may comprise a thermoset material. The
binder may comprise a radiation set material. As a percentage of a
weight of the first dry mixture, the first dry mixture may comprise
between about 80% to 95% activated carbon, between about 0% to 15%
conductive carbon, and between about 3% to 15% fibrillizable
fluoropolymer; and as percentage of weight of the second dry
mixture, the second dry mixture may comprise about 40% to 60%
binder, and about 40% to 60% conductive carbon. The first and
second dry mixtures may define a dry carbon film that comprises
about 1 to 100 parts of the second mixture for about every 1000
parts of the first dry mixture.
[0032] In one embodiment, a capacitor structure may comprise a
collector; and a plurality of dry processed particles coupled to
the collector, wherein the particles define a long integral dry
electrode film. The film may comprise dry conductive carbon and dry
adhesive materials. The film may comprise one or more blend of dry
particles. The particles may comprise activated carbon, conductive
carbon, and a fibrillizable binder; wherein a second of the
particles comprises conductive carbon and adhesive binder. As a
percentage of a weight of the film, the first of the particles may
comprise between about 80% to 95% activated carbon, between about
0% to 15% conductive carbon, and between about 3% to 15%
fibrillizable fluoropolymer; and as percentage of weight of the
film, the second of the particles may comprise about 40% to 60%
binder, and about 40% to 60% conductive carbon. The film may
comprise about 1 to 100 parts of the second of the particles for
about every 1000 parts of the first of the particles. The dry
particles may comprise conductive carbon, and a thermoplastic
binder. The film may be at least 5 meters long. The film may be
self-supporting. The adhesive materials may be selected from a
group consisting of thermoplastic, thermoset, and radiation set
materials.
[0033] In one embodiment, an electrode may comprise a collector;
and a dry process based electrode film, wherein the electrode film
is coupled to the collector, wherein the electrode film comprises
conductive and binder particles, and wherein between the collector
and the electrode film there exists only one distinct interface.
The binder particles may comprise a thermoplastic. The film may
further comprise activated carbon. The conductive particles may
comprise graphite. The conductive particles may comprise a
metal.
[0034] In one embodiment, an energy storage device electrode
comprises adhesive binder particles; and carbon particles, the
carbon particles comprising a surface, wherein a plurality of the
carbon particles are coupled to each other by the adhesive binder
particles, and wherein a plurality of the carbon particles make
direct carbon particle to carbon particle contact.
[0035] In one embodiment, an energy storage device structure
comprises a plurality of intermixed dry processed carbon and binder
particles formed into an electrode, wherein as compared to an
electrode formed of a plurality of the same carbon and binder
particles processed with a processing additive, the intermixed dry
processed carbon and binder particles comprises less residue.
[0036] In one embodiment, a capacitor comprises a continuous
compacted self supporting dry adhesive electrode film comprising a
dry mix of dry binder and dry carbon particles, the film coupled to
a collector, the collector shaped into a roll disposed within a
sealed aluminum housing. The dry adhesive electrode film may
comprise no processing additive. In one embodiment, an energy
storage device comprises dry process based adhesive electrode means
for providing adhesive and electrode functionality in an energy
storage device.
[0037] In one embodiment, a process for manufacturing a dry
electrode for use in an energy storage device product comprises the
steps of supplying dry carbon particles; supplying dry binder; dry
mixing the dry carbon particles and dry binder; and dry
fibrillizing the dry binder to create a matrix within which to
support the dry carbon particles as a dry material. The step of dry
fibrillizing may comprise application of sufficiently high-shear.
The high-shear may be applied in a jet-mill. The application of
sufficiently high-shear may be effectuated by application of a high
pressure. The high pressure may be applied as a high-pressure gas.
The gas may comprise oxygen. The pressure may be greater than or
equal to about 60 PSI. The gas may be applied at a dew point of
about -40 degrees F. 12 ppm. The process may further include a step
of compacting the dry material. In the process, the step of
compacting may be performed after one pass through a compacting
apparatus. The compacting apparatus may be a roll-mill. In one
embodiment, after the one pass though the compacting apparatus the
dry material comprises a self-supporting dry film. The
self-supporting dry film may comprise a thickness of about 100 to
250 microns. The self-supporting dry film may be formed as a
continuous sheet. The sheet may be one meter long. The dry material
may be manufactured without the use of any processing additives.
The processing additives not used may be hydrocarbons, high boiling
point solvents, antifoaming agents, surfactants, dispersion aids,
water, pyrrolidone mineral spirits, ketones, naphtha, acetates,
alcohols, glycols, toluene, xylene, and Isopars.TM.. The process
may include a step of calendering the dry material onto a
substrate. The substrate may comprise a collector. The collector
may comprise an aluminum foil. The dry material may calendered
directly onto the substrate without use of an intermediate layer.
The dry material may be calendered onto a treated substrate. The
dry binder may comprise a fibrillizable fluoropolymer. In one
embodiment, the dry material consists of the dry carbon particles
and the dry binder. The dry material may comprise between about 50%
to 99% activated carbon. The dry material may comprise between
about 0% to 25% conductive carbon. The dry material may comprise
between about 0.5% to 20% fluoropolymer particles. The dry material
may comprise between about 80% to 95% activated carbon and between
about 0% to 15% conductive carbon, and the dry binder may comprise
between about 3% to 15% fluoropolymer.
[0038] In one embodiment, a method of manufacturing an electrode
film may comprise the steps of mixing dry carbon and dry binder
particles; and forming a self-supporting film from the dry
particles without the use of any processing additives. The
processing additives not used may be hydrocarbons, high boiling
point solvents, antifoaming agents, surfactants, dispersion aids,
water, pyrrolidone mineral spirits, ketones, naphtha, acetates,
alcohols, glycols, toluene, xylene, and Isopars.TM..
[0039] In one embodiment, an energy storage device product, may
comprise a self-supporting film consisting of a dry mix of dry
carbon and dry binder particles. The dry mix may be a dry
fibrillized mix. The dry mix may comprise substantially no
processing additives. The processing additives not used may be
hydrocarbons, high boiling point solvents, antifoaming agents,
surfactants; dispersion aids, water, pyrrolidone mineral spirits,
ketones, naphtha, acetates, alcohols, glycols, toluene, xylene, and
Isopars.TM.. The dry mix may be dry fibrillized by application of a
high pressure. The high pressure may be applied by a high-pressure
gas. The high pressure may be applied by air with a dew point of
about -20 degrees F. 12 ppm.
[0040] In one embodiment an energy storage device product,
comprises one or more self-supporting dry film consisting of a dry
fibrillized mix of dry binder and dry carbon particles. The
self-supporting dry film may be compacted. The dry film may
comprise a thickness of 100 to 250 microns. The self-supporting dry
film may comprise a length of at least 1 meter. The self-supporting
dry film may be positioned against a substrate. The mix may
comprise between about 50% to 99% activated carbon. The mix may
comprise between about 0% to 25% conductive carbon. The mix may
comprise between about 0.5% to 20% fluoropolymer particles. The mix
may comprise between about 80% to 95% activated carbon and between
about 0% to 15% conductive carbon, and the dry binder may comprise
between about 3% to 15% fluoropolymer. The self-supporting film may
comprise no processing additives. The processing additives not used
may be hydrocarbons, high boiling point solvents, antifoaming
agents, surfactants, dispersion aids, water, pyrrolidone mineral
spirits, ketones, naphtha, acetates, alcohols, glycols, toluene,
xylene, and Isopars.TM.. The substrate may comprise a collector.
The collector may comprise aluminum. The product may comprise a
collector, wherein the dry film is positioned directly against a
surface of the collector. The dry mix may be dry fibrillized by a
high-pressure gas. The collector may comprise two sides, wherein
one self-supporting dry film is calendered directly against one
side of the collector, and wherein a second self-supporting dry
film is calendered directly against a second side of the collector.
The collector may be treated. The collector may be formed to
comprise a roll. The roll may be disposed within a sealed aluminum
housing. The housing may be disposed an electrolyte, wherein the
product comprises a double-layer capacitor.
[0041] In one embodiment, an energy storage product may consist of
a dry fibrillized mix of dry binder and dry carbon particles formed
into a continuous self supporting electrode film without the use of
any processing additives. The processing additives not used may
include high boiling point solvents, antifoaming agents,
surfactants, dispersion aids, water, pyrrolidone mineral spirits,
ketones, naphtha, acetates, alcohols, glycols, toluene, xylene, and
Isopars.TM..
[0042] In one embodiment, a capacitor comprises a film comprising a
dry fibrillized mix of dry binder and dry carbon particles, the
film coupled to a collector, the collector shaped into a roll, the
roll impregnated with an electrolyte and disposed within a sealed
aluminum housing. The film may comprise substantially no processing
additive. The film may consist of the dry carbon particles and the
dry binder. The film may comprise a long compacted self-supporting
dry film. The film may comprise a density of about 0.50 to 0.70
gm/cm.sup.2.
[0043] In one embodiment, an energy storage device comprises a dry
process based electrode means for providing conductive electrode
functionality in an energy storage device.
[0044] In one embodiment, a solventless method for manufacture of
an energy storage device electrode comprises the steps of providing
dry carbon particles; providing dry binder particles; and forming
the dry carbon and dry binder particles into an energy storage
device electrode without the use of any solvent.
[0045] In one embodiment, a solventless method for manufacture of
an energy storage device electrode comprises the steps of providing
dry carbon particles; providing dry binder particles; and
intermixing the dry carbon and dry binder particles to form an
energy storage device electrode without the use of any solvent.
[0046] In one embodiment, a solventless method for manufacture of
an energy storage device electrode comprises the steps of providing
dry carbon particles; providing dry binder particles; and forming
the dry carbon and dry binder particles into an energy storage
device electrode without the substantial use of any hydrocarbons,
high boiling point solvents, antifoaming agents, surfactants,
dispersion aids, water, pyrrolidone mineral spirits, ketones,
naphtha, acetates, alcohols, glycols, toluene, xylene, and/or
Isopars.TM..
[0047] In one embodiment, an energy storage device electrode
comprises substantial no hydrocarbons, high boiling point solvents,
antifoaming agents, surfactants, dispersion aids, water,
pyrrolidone mineral spirits, ketones, naphtha, acetates, alcohols,
glycols, toluene, xylene, and/or Isopars.TM..
[0048] Other embodiments, benefits, and advantages will become
apparent upon a further reading of the following Figures,
Description, and Claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1a is a block diagram illustrating a method for making
an energy storage device electrode film.
[0050] FIG. 1b is a high-level front view of a jet-mill assembly
used to fibrillize binder within a dry carbon particle mixture.
[0051] FIG. 1c is a high-level side view of a jet-mill assembly
shown in FIG. 1b;
[0052] FIG. 1d is a high-level top view of the jet-mill assembly
shown in FIGS. 1b and 1c.
[0053] FIG. 1e is a high-level front view of a compressor and a
compressed air storage tank used to supply compressed air to a
jet-mill assembly.
[0054] FIG. 1f is a high-level top view of the compressor and the
compressed air storage tank shown in FIG. 1e, in accordance with
the present invention.
[0055] FIG. 1g is a high-level front view of the jet-mill assembly
of FIGS. 1b-d in combination with a dust collector and a collection
container.
[0056] FIG. 1h is a high-level top view of the combination of FIGS.
1f and 1g.
[0057] FIGS. 1i, 1j, and 1k illustrate effects of variations in
feed rate, grind pressure, and feed pressure on tensile strength in
length, tensile strength in width, and dry resistivity of electrode
materials.
[0058] FIG. 1m illustrates effects of variations in feed rate,
grind pressure, and feed pressure on internal resistance.
[0059] FIG. 1n illustrates effects of variations in feed rate,
grind pressure, and feed pressure on capacitance of double layer
capacitors using electrodes.
[0060] FIG. 1p illustrates effect of variation in feed pressure on
internal resistance of electrodes, and on the capacitance.
[0061] FIG. 2a shows an apparatus for forming a structure of an
electrode.
[0062] FIG. 2b shows a degree of intermixing of dry particles.
[0063] FIG. 2c shows a gradient of particles within a dry film.
[0064] FIG. 2d shows a distribution of the sizes of dry binder and
conductive carbon particles.
[0065] FIGS. 2e-f, show carbon particles as encapsulated by
dissolved binder of the prior art and dry carbon particles as
attached to dry binder of the present invention.
[0066] FIG. 2g shows a system for forming a structure for use in an
energy storage device.
[0067] FIG. 3 is a side representation of one embodiment of a
system for bonding electrode films to a current collector for use
in an energy storage device.
[0068] FIG. 4a is a side representation of one embodiment of a
structure of an energy storage device electrode.
[0069] FIG. 4b is a top representation of one embodiment of an
electrode.
[0070] FIG. 5 is a side representation of a rolled electrode
coupled internally to a housing.
[0071] FIG. 6a shows capacitance vs. number of full
charge/discharge charge cycles.
[0072] FIG. 6b shows resistance vs. number of full charge/discharge
charge cycles.
[0073] FIG. 6c shows effects of electrolyte on specimens of
electrodes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0074] Reference will now be made in detail to several embodiments
of the invention that are illustrated in the accompanying drawings.
Wherever possible, same or similar reference numerals are used to
refer to the same or similar elements or steps used therein.
[0075] In accordance with embodiments of the present invention, an
inexpensive, long lasting, reliable dry particle capacitor,
capacitor electrode, and structures thereof, as well as methods for
making the same are described. The present invention provides
distinct advantages when compared to those of the additive-based
coating/extruder devices of the prior art.
[0076] The energy storage devices and methods associated with the
present invention do not use the one or more prior art processing
aides or additives associated with coating and extrusion based
processes (hereafter referred throughout as "processing additive"
and "additive"), including: added solvents, liquids, lubricants,
plasticizers, and the like. As well, one or more associated
additive removal steps, post coating treatments such as curing or
cross-linking, drying step(s) and apparatus associated therewith,
and the like, are eliminated. Because additives are not used during
manufacture, a final electrode product is not subject to chemical
interactions that may occur between the aforementioned prior art
residues of such additives and a subsequently used electrolyte.
Because binders that are dissolvable by additives do not need to be
used with present invention, a wider class of or selection of
binders may be used than in the prior art. Such binders can be
selected to be completely or substantially insoluble and
nonswellable in typically used electrolytes, an advantage, which
when combined with a lack of additive based impurities or residues
such electrolytes can react to, allows that a much more reliable
and durable energy storage device may be provided. A high
throughput method for making more durable and more reliable energy
storage devices is thus provided.
[0077] Referring now to FIG. 6a, there are seen capacitance vs.
number of full charge/discharge charge cycles tests for both a
prior art energy storage device 5 manufactured using processing
additives and an embodiment of an energy storage device 6
comprising structures manufactured using no processing additives
according to one or more of the principles described further
herein.
[0078] Device 5 incorporates in its design a prior art processing
additive-based electrode available from W.L Gore & Associates,
Inc. 401 Airport Rd., Elkton, Md. 21922, 410-392-444, under the
EXCELLERATOR.TM. brand of electrode. The EXCELLERATOR.TM. brand of
electrode was configured in a jellyroll configuration within an
aluminum housing to comprise a double-layer capacitor. Device 6 was
also configured as a similar Farad double-layer capacitor in a
similar form factor housing, but using instead a dry electrode film
33 (as referenced in FIG. 2g described below).
[0079] The dry electrode film 33 was adhered to a collector by an
adhesive coating sold under the trade name Electrodag.RTM. EB-012
by Acheson Colloids Company, 1600 Washington Ave., Port Huron,
M148060, Telephone 1-810-984-5581. Dry film 33 was manufactured
utilizing no processing additives in a manner described further
herein.
[0080] Those skilled in the art will identify that high capacitance
(for example, 1000 Farads and above) capacitor products that are
sold commercially are derated to reflect an initial drop (on the
order of 10% or so) in capacitance that may occur during the first
5000 or so capacitor charge discharge cycles, in other words, a
rated 2600 Farad capacitor sold commercially may initially be a
2900 Farad or higher rated capacitor. After the first 5000 cycles
or so, those skilled in the art will identify that under normal
expected use, (normal temperature, average cycle discharge duty
cycle, etc), a capacitors rated capacitance may decrease at a
predictable reduced rate, which may be used to predict a capacitors
useful life. The higher the initial capacitor value needed to
achieve a rated capacitor value, the more capacitor material is
needed, and thus, the higher the cost of the capacitor.
[0081] In the FIGS. 6a and 6b embodiments, both devices 5 and 6
were tested without any preconditioning. The initial starting
capacitance of devices 5 and 6 was about 2800 Farad. The test
conditions were such that at room temperature, both devices 5 and 6
were full cycle charged at 100 amps to 2.5 volts and then
discharged to 1.25 volts. Both devices were charged and discharged
in this manner continuously. The test was performed for
approximately 70,000 cycles for the prior art device 5, and for
approximately 120,000 cycles for the device 6. Those skilled in the
art will identify that such test conditions are considered to be
high stress conditions that capacitor products are not typically
expected to be subject to, but were nevertheless conducted to
demonstrate the durability of device 6. As indicated by the
results, the prior art device 5 experienced a drop of about 30% in
capacitance by the time 70,000 full charge cycles occurred, whereas
at 70,000 and 120,000 cycles device 6 experienced only a drop of
about 15% and 16%, respectively. Device 6 is shown to experience a
predictable decrease in capacitance that can be modeled to indicate
that cycling of the capacitor up to about 0.5 million, 1 million,
and 1.5 million cycles can be achieved under the specific
conditions with respective drops of 21%, 23%, and 24% in
capacitance. At 70,000 cycles it is shown that device 6 made
according to one or more of the embodiments disclosed herein
experienced about 50% less in capacitance drop than a processing
additive based prior art device 5 (about 15% vs. 30%,
respectively). At about 120,000 cycles it is shown that device 6
made according to one or more embodiments disclosed herein
experienced only about 17% capacitance drop. At 1 million cycles it
is envisioned that device 6 will experience less than 25% drop from
its initial capacitance.
[0082] Referring now to FIG. 6b, there are seen resistance vs.
number of full charge/discharge charge cycles tests for both a
prior art energy storage device 5 manufactured using processing
additives and an embodiment of an energy storage device 6. As
indicated by the results the prior art device 5 experienced an
increase in resistance over that of device 6. As seen, device 6
experiences a minimal increase in resistance (less than 10% over
100,000 cycles) as compared to device 5 (100% increase over 75,000
cycles).
[0083] Referring now to FIG. 6c, there are seen physical specimens
of electrode obtained from devices 5, 6, and 7 shown after one week
and 1 month of immersion in 1.5 M tetramethylammonium or
tetrafluoroborate in acetonitrile electrolyte at a temperature of
85 degrees centigrade. The electrode sample from device 5 comprises
the processing additive based EXCELLERATOR.TM. brand of electrode
film discussed above, and the electrode sample of device 7
comprises a processing additive based electrode film obtained from
a 5 Farad NESCAP double-layer capacitor product, Wonchun-Dong 29-9,
Paldal-Ku, Suwon, Kyonggi, 442-380, Korea, Telephone: +82 31 219
0682. As seen, electrodes from devices 5 and 7 show damage after 1
week and substantial damage after 1 month immersion in acetonitrile
electrolyte. In contrast, an electrode from a device 6 made of one
or more of the embodiments described further herein shows no visual
damage, even after one year (physical specimen not shown) of
immersion in acetonitrile electrolyte.
[0084] Accordingly, in one embodiment, when charged at 100 amps to
2.5 volts and then discharged to 1.25 volts over 120,000 cycles a
device 6 experiences less than a 30 percent drop in capacitance. In
one embodiment, when charged at 100 amps to 2.5 volts and then
discharged to 1.25 volts over 70,000 cycles a device 6 experiences
less than a 30 percent drop in capacitance. In one embodiment, when
charged at 100 amps to 2.5 volts and then discharged to 1.25 volts
over 70,000 cycles a device 6 experiences less than a 5 percent
drop in capacitance in one embodiment, a device 6 is capable of
being charged at 100 amps to 2.5 volts and then discharged to 1.25
volts over 1,000,000 cycles with less than a 30% drop in
capacitance. In one embodiment, a device 6 is capable of being
charged at 100 amps to 2.5 volts and then discharged to 1.25 volts
over 1,500,000 cycles with less than a 30% drop in capacitance. In
one embodiment, when charged at 100 amps to 2.5 volts and then
discharged to 1.25 volts over 70,000 cycles a device 6 experiences
an increase in resistance of less than 100 percent. In one
embodiment, a method of using a device 6 comprises the steps of:
(a) charging the device from 1.25 volts to 2.5 volts at 100 amps;
(b) discharging the device to 1.25 volts; and (c) measuring less
than a 30% drop in an initial capacitance of the device after
repeating step (a) and step (b) 70,000 times. In one embodiment, a
method of using a device 6 comprises the steps of: (a) charging the
device from 1.25 volts to 2.5 volts at 100 amps; (b) discharging
the device to 1.25 volts; and (c) measuring less than a 5% drop in
an initial capacitance of the device after repeating step (a) and
step (b) 70,000 times.
[0085] In the embodiments that follow, it will be understood that
reference to no-use and non-use of additive(s) in the manufacture
of an energy storage device according to the present invention
takes into account that electrolyte may be used during a final
electrode electrolyte immersion/impregnation step. An electrode
electrolyte immersion/impregnation step is typically utilized prior
to providing a final finished capacitor electrode in a sealed
housing. Furthermore, even though additives, such as solvents,
liquids, and the like, are not used in the manufacture of
embodiments disclosed herein, during manufacture, a certain amount
of impurity, for example, moisture, may be absorbed or attach
itself from a surrounding environment. Those skilled in the art
will understand that the dry particles used with embodiments and
processes disclosed herein may also, prior to their being provided
by particle manufacturers as dry particles, have themselves been
pre-processed with additives and, thus, comprise one or more
pre-process residue. For these reasons, despite the non-use of
additives, one or more of the embodiments and processes disclosed
herein may require a drying step (which, if performed with
embodiments of the present invention, can be much shorter than the
drying steps of the prior art) prior to a final electrolyte
impregnation step so as to remove/reduce such aforementioned
pre-process residues and impurities. It is identified that even
after one or more drying step, trace amounts of the aforementioned
pre-process residues and impurities may be present in the prior
art, as well as embodiments described herein.
[0086] In general, because both the prior art and embodiments of
the present invention obtain base particles and materials from
similar manufacturers, and because they both may be exposed to
similar pre-process environments, measurable amounts of prior art
pre-process residues and impurities may be similar in magnitude to
those of embodiments of the present invention, although variations
may occur due to differences in pre-processes, environmental
effects, etc. In the prior art, the magnitude of such pre-process
residues and impurities is smaller than that of the residues and
impurities that remain and that can be measured after processing
additives are used. This measurable amount of processing additive
based residues and impurities can be used as an indicator that
processing additives have been used in a prior art energy storage
device product. The lack of such measurable amounts of processing
additive can as well be used to distinguish the non-use of
processing additives in embodiments of the present invention.
[0087] Table 1 indicates the results of a chemical analysis of a
prior art electrode film and an embodiment of a dry electrode film
made in accordance with principles disclosed further herein. The
chemical analysis was conducted by Chemir Analytical Services, 2672
Metro Blvd., Maryland Heights, Mo. 63043, Phone 314-291-6620. Two
samples were analyzed with a first sample (Chemir 533572) comprised
of finely ground powder obtained from a prior art additive based
electrode film sold under the EXCELLERATOR.TM. brand of electrode
film by W.L Gore & Associates, Inc. 401 Airport Rd., Elkton,
Md. 21922, 410-392-444, which in one embodiment is referenced under
part number 102304. A second sample (Chemir 533571) comprised a
thin black sheet of material cut into 1/8 to 1 inch sided
irregularly shaped pieces obtained from a dry film 33 (as discussed
in FIG. 2g below). The second sample (Chemir 533571) comprised a
particle mixture of about 80% to 90% activated carbon, about 0% to
15% conductive carbon, and about 3% to 15% PTFE binder by weight.
Suitable carbon powders are available from a variety of sources,
including YP-17 activated carbon particles sold by Kuraray Chemical
Co., LTD, Shin-hankyu Bldg. 9F Blvd. C-237, 1-12-39 Umeda,
Kiata-ku, Osaka 530-8611, Japan; and BP 2000 conductive particles
sold by Cabot Corp. 157 Concord Road, P.O. Box 7001, Billerica,
Mass. 01821-7001, Phone: 978 663-3455. A tared portion of prior art
sample Chemir 53372 was transferred to a quartz pyrolysis tube. The
tube with its contents was placed inside of a pyrolysis probe. The
probe was then inserted into a valved inlet of a gas chromatograph.
The effluent of the column was plumbed directly into a mass
spectrometer that served as a detector. This configuration allowed
the sample in the probe to be heated to a predetermined temperature
causing volatile analytes to be swept by a stream of helium gas
into the gas into the gas chromatograph and through the analytical
column, and to be detected by the mass spectrometer. The pyrolysis
probe was flash heated from ambient temperature at a rate of 5
degrees C./millisecond to 250 degrees C. and held constant for 30
seconds. The gas chromatograph was equipped with a 30 meter Agilent
DB-5 analytical column. The gas chromatograph oven temperature was
as follows: the initial temperature was held at 45 degrees C. for 5
minutes and then was ramped at 20 degrees C. to 300 degrees C. and
held constant for 12.5 minutes. A similar procedure was conducted
for sample 53371 of a dry film 33. Long chain branched hydrocarbon
olefins were detected in both samples, with 2086 parts per million
(PPM) detected in the prior art sample, and with 493 PPM detected
in dry film 33. Analytes dimethylamine and a substituted alkyl
propanoate were detected in sample Chemir 53372 with 337 PPM and
were not detected in sample Chemir 53371. It is envisioned that
future analysis of other prior art additive based electrode films
will provide similar results with which prior art use of processing
additives, or equivalently, the non-use of additives of embodiments
described herein, can be identified and distinguished.
[0088] One or more prior art additives, impurities, and residues
that exist in, or are utilized by, and that may be present in lower
quantities in embodiments of the present invention than the prior
art, include: hydrocarbons, high boiling point solvents,
antifoaming agents, surfactants, dispersion aids, water,
pyrrolidone mineral spirits, ketones, naphtha, acetates, alcohols,
glycols, toluene, xylene, Isopars.TM., plasticizers, and the like.
TABLE-US-00001 TABLE 1 Pyrolysis GC/MS Analysis Retention Chemir
53372 Time in Minutes Chemir 53371 (Prior Art) 1.65 0 PPM 0 PPM
12.3 0 PPM 0 PPM 13.6 0 PPM Butylated hydroxyl toluene 337 PPM 20.3
0 PPM 0 PPM 20.6 A long chain A long chain branched branched
hydrocarbon hydrocarbon olefin 493 PPM 2086 PPM
[0089] Referring now to FIG. 1a, a block diagram illustrating a
process for making a dry particle based energy storage device is
shown. As used herein, the term "dry" implies non-use of additives
during process steps described herein, other than during a final
impregnating electrolyte step. The process shown in FIG. 1a begins
by blending dry carbon particles and dry binder together. As
previously discussed, one or more of such dry carbon particles, as
supplied by carbon particle manufacturers for use herein, may have
been pre-processed. Those skilled in the art will understand that
depending on particle size, particles can be described as powders
and the like, and that reference to particles is not meant to be
limiting to the embodiments described herein, which should be
limited only by the appended claims or their equivalents. For
example, within the scope of the term "particles," the present
invention contemplates powders, spheres, platelets, flakes, fibers,
nano-tubes and other particles with other dimensions and other
aspect ratios. In one embodiment, dry carbon particles as
referenced herein refers to activated carbon particles 12 and/or
conductive particles 14, and binder particles 16 as referenced
herein refers to an inert dry binder. In one embodiment, conductive
particles 14 comprise conductive carbon particles. In one
embodiment, conductive particles 14 comprise conductive graphite
particles. In one embodiment, it is envisioned that conductive
particles 14 comprise a metal powder or the like. In one
embodiment, dry binder 16 comprises a fibrillizable fluoropolymer,
for example, polytetrafluoroethylene (PTFE) particles. Other
possible fibrillizable binders include ultra-high molecular weight
polypropylene, polyethylene, co-polymers, polymer blends and the
like. It is understood that the present invention should not be
limited by the disclosed or suggested particles and binder, but
rather, by the claims that follow. In one embodiment, particular
mixtures of particles 12, 14, and binder 16 comprise about 50% to
99% activated carbon, about 0% to 25% conductive carbon, and/or
about 0.5% to 50% binder by weight. In a more particular
embodiment, particle mixtures include about 80% to 90% activated
carbon, about 0% to 15% conductive carbon, and about 3% to 15%
binder by weight. In one embodiment, the activated carbon particles
12 comprise a mean diameter of about 10 microns. In one embodiment,
the conductive carbon particles 14 comprise diameters less than 20
microns. In one embodiment, the binder particles 16 comprise a mean
diameter of about 450 microns. Suitable carbon powders are
available from a variety of sources, including YP-17 activated
carbon particles sold by Kuraray Chemical Co., LTD, Shin-hankyu
Bldg. 9F Blvd. C-237, 1-12-39 Umeda, Kiata-ku, Osaka 530-8611,
Japan; and BP 2000 conductive particles sold by Cabot Corp. 157
Concord Road, P.O. Box 7001, Billerica, Mass. 01821-7001, Phone:
978 663-3455.
[0090] In step 18, particles of activated carbon, conductive
carbon, and binder provided during respective steps 12, 14, and 16
are dry blended together to form a dry mixture. In one embodiment,
dry particles 12, 14, and 16 are blended for 1 to 10 minutes in a
V-blender equipped with a high intensity mixing bar until a uniform
dry mixture is formed. Those skilled in the art will identify that
blending time can vary based on batch size, materials, particle
size, densities, as well as other properties, and yet remain within
the scope of the present invention. With reference to blending step
18, in one embodiment, particle size reduction and classification
can be carried out as part of the blending step 18, or prior to the
blending step 18. Size reduction and classification may improve
consistency and repeatability of the resulting blended mixture and,
consequently, of the quality of the electrode films and electrodes
fabricated from the dry blended mixture.
[0091] After dry blending step 18, dry binder 16 within the dry
particles is fibrillized in a dry fibrillizing step 20. The dry
fibrillizing step 20 is effectuated using a dry solventless and
liquidless high shear technique. During dry fibrillizing step 20,
high shear forces are applied to dry binder 16 in order to
physically stretch it. The stretched binder forms a network of thin
web-like fibers that act to enmesh, entrap, bind, and/or support
the dry particles 12 and 14. In one embodiment, fibrillizing step
20 may be effectuated using a jet-mill.
[0092] Referring to now to FIGS. 1b, 1c, and 1d, there is seen,
respectively, front, side, and top views of a jet-mill assembly 100
used to perform a dry fibrillization step 20. For convenience, the
jet-mill assembly 100 is installed on a movable auxiliary equipment
table 105, and includes indicators 110 for displaying various
temperatures and gas pressures that arise during operation. A gas
input connector 115 receives compressed air from an external supply
and routes the compressed air through internal tubing (not shown)
to a feed air hose 120 and a grind air hose 125, which both lead
and are connected to a jet-mill 130. The jet-mill 130 includes: (1)
a funnel-like material receptacle device 135 that receives
compressed feed air from the feed air hose 120, and the blended
carbon-binder mixture of step 18 from a feeder 140; (2) an internal
grinding chamber where the carbon-binder mixture material is
processed; and (3) an output connection 145 for removing the
processed material. In the illustrated embodiment, the jet-mill 130
is a 4-inch Micronizere model available from Sturtevant, Inc., 348
Circuit Street, Hanover, Mass. 02339; telephone number (781)
829-6501. The feeder 140 is an AccuRate.RTM. feeder with a digital
dial indicator model 302M, available from Schenck AccuRate.RTM.,
746 E. Milwaukee Street, P.O. Box 208, Whitewater, Wis. 53190;
telephone number (888) 742-1249. The feeder includes the following
components: a 0.33 cubic ft. internal hopper; an external paddle
agitation flow aid; a 1.0-inch, full pitch, open flight feed screw;
a % hp, 90VDC, 1,800 rpm, TENV electric motor drive; an internal
mount controller with a variable speed, 50:1 turndown ratio; and a
110 Volt, single-phase, 60 Hz power supply with a power cord. The
feeder 140 dispenses the carbon-binder mixture provided by step 18
at a preset rate. The rate is set using the digital dial, which is
capable of settings between 0 and 999, linearly controlling the
feeder operation. The highest setting of the feeder dial
corresponds to a feeder output of about 12 kg per hour.
[0093] The feeder 140 appears in FIGS. 1b and 1d, but has been
omitted from FIG. 1c, to prevent obstruction of view of other
components of the jet-mill 130. The compressed air used in the
jet-mill assembly 100 is provided by a combination 200 of a
compressor 205 and a compressed air storage tank 210, illustrated
in FIGS. 1e and 1f; FIG. 1e is a front view and FIG. 1f is a top
view of the combination 200. The compressor 205 used in this
embodiment is a GA 30-55C model available from Atlas Copco
Compressors, Inc., 161 Lower Westfield Road, Holyoke, Mass. 01040;
telephone number (413) 536-0600. The compressor 205 includes the
following features and components: air supply capacity of 180
standard cubic feet per minute ("SCFM") at 125 PSIG; a 40-hp,
3-phase, 60 HZ, 460 VAC premium efficiency motor; a WYE-delta
reduced voltage starter; rubber isolation pads; a refrigerated air
dryer; air filters and a condensate separator; an air cooler with
an outlet 206; and an air control and monitoring panel 207. The
180-SCFM capacity of the compressor 205 is more than sufficient to
supply the 4-inch Micronizer.RTM. jet-mill 130, which is rated at
55 SCFM. The compressed air storage-tank 210 is a 400-gallon
receiver tank with a safety valve, an automatic drain valve, and a
pressure gauge. The compressor 205 provides compressed air to the
tank 205 through a compressed air outlet valve 206, a hose 215, and
a tank inlet valve 211.
[0094] It is identified that the compressed air provided under
high-pressure by compressor 205 is preferably as dry as possible.
Thus, in one embodiment, an appropriately placed in-line filter
and/or dryer may be added. In one embodiment, a range of acceptable
dew point for the air is about -20 to -40 degrees F., and a water
content of less than 20 ppm. Although discussed as being
effectuated by high-pressure air, it is understood that other
sufficiently dry gases are envisioned as being used to fibrillize
binder particles utilized in embodiments of the present invention,
for example, oxygen, nitrogen, helium, and the like.
[0095] In the jet-mill 130, the carbon-binder mixture is inspired
by venturi and transferred by the compressed feed air into a
grinding chamber, where the fibrillization of the mixture takes
place. In one embodiment, the grinding chamber is lined with a
ceramic such that abrasion of the internal walls of the jet-mill is
minimized and so as to maintain purity of the resulting jet-milled
carbon-binder mixture. The grinding chamber, which has a generally
cylindrical shape, includes one or more nozzles placed
circumferentially. The nozzles discharge the compressed grind air
that is supplied by the grind air hose 125. The compressed air jets
injected by the nozzles accelerate the carbon-binder particles and
cause predominantly particle-to-particle collisions, although some
particle-wall collisions also take place. The collisions dissipate
the energy of the compressed air relatively quickly, fibrillizing
the dry binder 16 within the mixture and embedding carbon particle
12 and 14 aggregates and agglomerates into the lattice formed by
the fibrillized binder. The collisions may also cause size
reduction of the carbon aggregates and agglomerates. The colliding
particles 12, 14, and 16 spiral towards the center of the grinding
chamber and exit the chamber through the output connection 145.
[0096] Referring now to FIGS. 1g and 1h, there are seen front and
top views, respectively, of the jet-mill assembly 100, a dust
collector 160, and a collection container 170 (further referenced
in FIG. 2a as container 20). In one embodiment, the fibrillized
carbon-binder particles that exit through the output connection 145
are guided by a discharge hose 175 from the jet-mill 130 into a
dust collector 160. In the illustrated embodiment, the dust
collector 160 is model CL-7-36-11 available from Ultra Industries,
Inc., 1908 DeKoven Avenue, Racine, Wis. 53403; telephone number
(262) 633-5070. Within the dust collector 160 the output of the
jet-mill 130 is separated into (1) air, and (2) a dry fibrillized
carbon-binder particle mixture 20. The carbon-binder mixture is
collected in the container 170, while the air is filtered by one or
more filters and then discharged. The filters, which may be
internal or external to the dust collector 160, are periodically
cleaned, and the dust is discarded. Operation of the dust collector
is directed from a control panel 180.
[0097] It has been identified that a dry compounded material, which
is provided by dry fibrillization step 20, retains its homogeneous
particle like properties for a limited period of time. In one
embodiment, because of forces, for example, gravitational forces
exerted on the dry particles 12, 14, and 16, the compounded
material begins to settle such that spaces and voids that exist
between the dry particles 12, 14, 16 after step 20 gradually become
reduced in volume. In one embodiment, after a relatively short
period of time, for example 10 minutes or so, the dry particles 12,
14, 16 compact together and begin to form clumps or chunks such
that the homogeneous properties of the compounded material may be
diminished and/or such that downstream processes that require free
flowing compounded materials are made more difficult or impossible
to achieve. Accordingly, in one embodiment, it is identified that a
dry compounded material as provided by step 20 should be utilized
before its homogeneous properties are no longer sufficiently
present and/or that steps are taken to keep the compounded material
sufficiently aerated to avoid clumping.
[0098] It should be noted that the specific processing components
described so far may vary as long as the intent of the embodiments
described herein is achieved. For example, techniques and machinery
that are envisioned for potential use to provide high shear forces
to effectuate a dry fibrillization step 20 include jet-milling, pin
milling, impact pulverization, and hammer milling, and other
techniques and apparatus. Further in example, a wide selection of
dust collectors can be used in alternative embodiments, ranging
from simple free-hanging socks to complicated housing designs with
cartridge filters or pulse-cleaned bags. Similarly, other feeders
can be easily substituted in the assembly 100, including
conventional volumetric feeders, loss-weight volumetric feeders,
and vibratory feeders. The size, make, and other parameters of the
jet-mill 130 and the compressed air supply apparatus (the
compressor 205 and the compressed air storage tank 210) may also
vary and yet be within the scope of the present invention.
[0099] The present inventors have performed a number of experiments
to investigate the effects of three factors in the operation of
jet-mill assembly 100 on qualities of the dry compounded material
provided by dry fibrillization step 20, and on compacted/calendered
electrode films fabricated therefrom. The three factors are these:
(1) feed air pressure, (2) grind air pressure, and (3) feed rate.
The observed qualities included tensile strength in width (i.e., in
the direction transverse to the direction of movement of a dry
electrode film in a high-pressure calender during a compacting
process); tensile strength in length (i.e., in the direction of the
dry film movement); resistivity of the jet-mill processed mixture
provided by dry fibrillization step 20; internal resistance of
electrodes made from the dry electrode film in a double layer
capacitor application; and specific capacitance achieved in a
double layer capacitor application. Resistance and specific
capacitance values were obtained for both charge (up) and discharge
(down) capacitor cycles.
[0100] The design of experiments ("DOE") included a
three-factorial, eight experiment investigation performed with dry
electrode films dried for 3 hours under vacuum conditions at 160
degrees Celsius. Five or six samples were produced in each of the
experiments, and values measured on the samples of each experiment
were averaged to obtain a more reliable result. The three-factorial
experiments included the following points for the three
factors:
[0101] 1. Feed rate was set to indications of 250 and 800 units on
the feeder dial used. Recall that the feeder rate has a linear
dependence on the dial settings, and that a full-scale setting of
999 corresponds to a rate of production of about 12 kg per hour
(and therefore a substantially similar material consumption rate).
Thus, settings of 250 units corresponded to a feed rate of about 3
kg per hour, while settings of 800 units corresponded to a feed
rate of about 9.6 kg per hour. In accordance with the standard
vernacular used in the theory of design of experiments, in the
accompanying tables and graphs the former setting is designated as
a "0" point, and the latter setting is designated as a "1"
point.
[0102] 2. The grind air pressure was set alternatively to 85 psi
and 110 psi, corresponding, respectively, to "0" and "1" points in
the accompanying tables and graphs.
[0103] 3. The feed air pressure (also known as inject air pressure)
was set to 60 and 70 psi, corresponding, respectively, to "0" and
"1" points.
[0104] Turning first to tensile strength measurements, strips of
standard width were prepared from each sample, and the tensile
strength measurement of each sample was normalized to a one-mil
thickness. The results for tensile strength measurements in length
and in width appear in Tables 2 and 3 below. TABLE-US-00002 TABLE 2
Tensile Strength in Length FACTORS SAMPLE TENSILE NORMALIZED )Feed
Rate, Grind DOE THICKNESS STRENGTH IN TENSILE STRENGTH Exp. No.
psi, Feed psi) POINTS (mil) LENGTH (grams) IN LENGTH (g/mil) 1
250/85/60 0/0/0 6.1 123.00 20.164 2 250/85/70 0/0/1 5.5 146.00
26.545 3 250/110/60 0/1/0 6.2 166.00 26.774 4 250/110/70 0/1/1 6.1
108.00 17.705 5 800/85/60 1/0/0 6.0 132.00 22.000 6 800/85/70 1/0/1
5.8 145.00 25.000 7 800/110/60 1/1/0 6.0 135.00 22.500 8 800/110/70
1/1/1 6.2 141.00 22.742
[0105] TABLE-US-00003 TABLE 3 Tensile Strength in Width Factors
Sample Tensile Normalized (Feed Rate, Grind DOE Thickness Strength
in Tensile Strength Exp. No psi, Feed psi) Points (mil) Length
(grams) in Length (g/mil) 1 250/85/60 0/0/0 6.1 63.00 10.328 2
250/85/70 0/0/1 5.5 66.00 12.000 3 250/110/60 0/1/0 6.2 77.00
12.419 4 250/110/70 0/1/1 6.1 59.00 9.672 5 800/85/60 1/0/0 6.0
58.00 9.667 6 800/85/70 1/0/1 5.8 70.00 12.069 7 800/110/60 1/1/0
6.0 61.00 10.167 8 800/110/70 1/1/1 6.2 63.00 10.161
[0106] Table 4 below presents resistivity measurements of a
jet-mill-dry blend of particles provided by dry fibrillization step
20. Note that the resistivity measurements were taken before the
mixture was processed into a dry electrode film. TABLE-US-00004
TABLE 4 Dry Resistance DRY Factors DOE RESISTANCE Exp. No. (Feed
Rate, Grind psi, Feed psi) Points (Ohms) 1 250/85/60 0/0/0 0.267 2
250/85/70 0/0/1 0.229 3 250/110/60 0/1/0 0.221 4 250/110/70 0/1/1
0.212 5 800/85/60 1/0/0 0.233 6 800/85/70 1/0/1 0.208 7 800/110/60
1/1/0 0.241 8 800/110/70 1/1/1 0.256
[0107] Referring now to FIGS. 1i, 1j, and 1k, there are illustrated
the effects of the three factors on the tensile strength in length,
tensile strength in width, and dry resistivity. Note that each
end-point for a particular factor line (i.e., the feed rate line,
grind pressure line, or inject pressure line) on a graph
corresponds to a measured value of the quality parameter (i.e.,
tensile strength or resistivity) averaged over all experiments with
the particular key factor held at either "0" or "1," as the case
may be. Thus, the "0" end-point of the feed rate line (the left
most point) represents the tensile strength averaged over
experiments numbered 1-4, while the "1" end-point on the same line
represents the tensile strength averaged over experiments numbered
4-8. As can be seen from FIGS. 1i and 1j, increasing the inject
pressure has a moderate to large positive effect on the tensile
strength of an electrode film. At the same time, increasing the
inject pressure has the largest effect on the dry resistance of the
powder mixture, swamping the effects of the feed rate and grind
pressure. The dry resistance decreases with increasing the inject
pressure. Thus, all three qualities benefit from increasing the
inject pressure.
[0108] In Table 5 below we present data for final capacitances
measured in double-layer capacitors utilizing dry electrode films
made from dry fibrillized particles as described herein by each of
the 8 experiments, averaged over the sample size of each
experiment. Note that C.sub.up refers to the capacitances measured
when charging double-layer capacitors, while C.sub.down values were
measured when discharging the capacitors. As in the case of tensile
strength data, the capacitances were normalized to the thickness of
the electrode film. In this case, however, the thicknesses have
changed, because the dry film has undergone compression in a
high-pressure nip during the process of bonding the film to a
current collector. It is noted in obtaining the particular results
of Table 5, the dry electrode film was bonded to a current
collector by an intermediate layer of adhesive. Normalization was
carried out to the standard thickness of 0.150 millimeters.
TABLE-US-00005 TABLE 5 C.sub.up and C.sub.down Factors Sample
Normalized NORMALIZED (Feed Rate, Grind DOE Thickness C.sub.up
C.sub.up C.sub.down C.sub.down Exp. No. psi, Feed psi) Points (mm)
(Farads) (Farads) (Farads) (Farads) 1 250/85/60 0/0/0 0.149 1.09
1.097 1.08 1.087 2 250/85/70 0/0/1 0.133 0.98 1.105 0.97 1.094 3
250/110/60 0/1/0 0.153 1.12 1.098 1.11 1.088 4 250/110/70 0/1/1
0.147 1.08 1.102 1.07 1.092 5 800/85/60 1/0/0 0.148 1.07 1.084 1.06
1.074 6 800/85/70 1/0/1 0.135 1.00 1.111 0.99 1.100 7 800/110/60
1/1/0 0.150 1.08 1.080 1.07 1.070 8 800/110/70 1/1/1 0.153 1.14
1.118 1.14 1.118
[0109] In Table 6 we present data for resistances measured in each
of the 8 experiments, averaged over the sample size of each
experiment. Similarly to the previous table, R.sub.up designates
resistance values measured when charging double-layer capacitors,
while R.sub.down refers to resistance values measured when
discharging the capacitors. TABLE-US-00006 TABLE 6 R.sub.up and
R.sub.down Factors (Feed Rate, Sample Electrode Electrode Exp.
Grind psi, DOE Thickness Resistance Resistance No. Feed psi) Points
(mm) R.sub.up (Ohms) R.sub.down (Ohms) 1 250/85/60 0/0/0 0.149 1.73
1.16 2 250/85/70 0/0/1 0.133 1.67 1.04 3 250/110/60 0/1/0 0.153
1.63 1.07 4 250/110/70 0/1/1 0.147 1.64 1.07 5 800/85/60 1/0/0
0.148 1.68 1.11 6 800/85/70 1/0/1 0.135 1.60 1.03 7 800/110/60
1/1/0 0.150 1.80 1.25 8 800/110/70 1/1/1 0.153 1.54 1.05
[0110] To help visualize the above data and identify the data
trends, we present FIGS. 1m and 1n, which graphically illustrate
the relative importance of the three factors on the resulting
R.sub.down and normalized C.sub.up. Note that in FIG. 1m the Feed
Rate and the Grind Pressure lines are substantially coincident.
[0111] Once again, increasing the inject pressure benefits both
electrode resistance R.sub.down (lowering it), and the normalized
capacitance C.sub.up (increasing it). Moreover, the effect of the
inject pressure is greater than the effects of the other two
factors. In fact, the effect of the inject pressure on the
normalized capacitance overwhelms the effects of the feed rate and
the grind pressure factors, at least for the factor ranges
investigated.
[0112] Additional data has been obtained relating C.sub.up and
R.sub.down to further increases in the inject pressure. Here, the
feed rate and the grind pressure were kept constant at 250 units
and 110 psi, respectively, while the inject pressure during
production was set to 70 psi, 85 psi, and 100 psi. Bar graphs in
FIG. 1p illustrate these data. As can be seen from these graphs,
the normalized capacitance C.sub.up was little changed with
increasing inject pressure beyond a certain point, while electrode
resistance displayed a drop of several percentage points when the
inject pressure was increased from 85 psi to 100 psi. The inventors
herein believe that increasing the inject pressure beyond 100 psi
would further improve electrode performance, particularly by
decreasing internal electrode resistance.
[0113] Although dry blending 18 and dry fibrillization step 20 have
been discussed herein as two separate steps that utilize multiple
apparatus, it is envisioned that steps 18 and 20 could be conducted
in one step wherein one apparatus receives dry particles 12, 14,
and/or 16 as separate streams to mix the particles and thereafter
fibrillize the particles. Accordingly, it is understood that the
embodiments herein should not be limited by steps 18 and 20, but by
the claims that follow. Furthermore, the preceding paragraphs
describe in considerable detail inventive methods for dry
fibrillizing carbon and binder mixtures to fabricate dry films,
however, neither the specific embodiments of the invention as a
whole, nor those of its individual features should limit the
general principles described herein, which should be limited only
by the claims that follow.
[0114] It is identified that, in order to form a self supporting
dry film with adequate physical as well as electrical properties
for use in a capacitor as described further herein, sufficiently
high shear forces are needed. In contrast to the additive-based
prior art fibrillization steps, the present invention provides such
shear forces without using processing aides or additives.
Furthermore, with the present invention no additives are used
before, during, or after application of the shear forces. Numerous
benefits derive from non-use of prior art additives including:
reduction of process steps and processing apparatus, increase in
throughput and performance, the elimination or substantial
reduction of residue and impurities that can derive from the use of
additives and additive-based process steps, as well as other
benefits that are discussed or that can be understood by those
skilled in the art from the description of the embodiments that
follows.
[0115] Referring back to FIG. 1a, the illustrated process also
includes steps 21 and 23, wherein dry conductive particles 21 and
dry binder 23 are blended in a dry blend step 19. Step 19, as well
as possible step 26, also do not utilize additives before, during,
or after the steps. In one embodiment, dry conductive particles 21
comprise conductive carbon particles. In one embodiment, dry
conductive particles 21 comprise conductive graphite particles. In
one embodiment, it is envisioned that conductive particles may
comprise a metal powder of the like. In one embodiment, dry binder
23 comprises a dry thermoplastic material. In one embodiment, the
dry binder comprises non-fibrillizable fluoropolymer. In one
embodiment, dry binder 23 comprises polyethylene particles. In one
embodiment, dry binder 23 comprises polypropylene or polypropylene
oxide particles. In one embodiment, the thermoplastic material is
selected from polyolefin classes of thermoplastic known to those
skilled in the art. Other thermoplastics of interest and envisioned
for potential use include homo and copolymers, olefinic oxides,
rubbers, butadiene rubbers, nitrile rubbers, polyisobutylene,
poly(vinylesters), poly(vinylacetates), polyacrylate, fluorocarbon
polymers, with a choice of thermoplastic dictated by its melting
point, metal adhesion, and electrochemical and solvent stability in
the presence of a subsequently used electrolyte. In other
embodiments, thermoset and/or radiation set type binders are
envisioned as being useful. The present invention, therefore,
should not be limited by the disclosed and suggested binders, but
only by the claims that follow.
[0116] As has been stated, a deficiency in the additive-based prior
art is that residues of additive, impurities, and the like remain,
even after one or more long drying step(s). The existence of such
residues is undesirable for long-term reliability when a subsequent
electrolyte impregnation step is performed to activate an energy
storage device electrode. For example, when an acetonitrile-based
electrolyte is used, chemical and/or electrochemical interactions
between the acetonitrile and residues and impurities can cause
undesired destructive chemical processes in, and/or a swelling of,
an energy storage device electrode. Other electrolytes of interest
include carbonate-based electrolytes (ethylene carbonate, propylene
carbonate, dimethylcarbonate), alkaline (KOH, NaOH), or acidic
(H2SO4) water solutions. It is identified when processing additives
are substantially reduced or eliminated from the manufacture of
energy storage device structures, as with one or more of the
embodiments disclosed herein, the prior art undesired destructive
chemical and/or electrochemical processes and swelling caused by
the interactions of residues and impurities with electrolyte are
substantially reduced or eliminated.
[0117] In one embodiment, dry carbon particles 21 and dry binder
particles 23 are used in a ratio of about 40%-60% binder to about
40%-60% conductive carbon by weight. In step 19, dry carbon
particles 21 and dry binder material 23 are dry blended in a
V-blender for about 5 minutes. In one embodiment, the conductive
carbon particles 21 comprise a mean diameter of about 10 microns.
In one embodiment, the binder particles 23 comprise a mean diameter
of about 10 microns or less. Other particle sizes are also within
the scope of the invention, and should be limited only by the scope
of the claims. In one embodiment, (further disclosed by FIG. 2a),
the blend of dry particles provided in step 19 is used in a dry
feed step 22. In one embodiment (further disclosed by FIG. 2g), the
blend of dry particles in step 19 may be used in a dry feed step
29, instead of dry feed step 22. In order to improve suspension and
characteristics of particles provided by container 19, a small
amount of fibrillizable binder (for example binder 16) may be
introduced into the mix of the dry carbon particles 21 and dry
binder particles 23, and dry fibrillized in an added dry
fibrillization step 26 prior to a respective dry feed step 22 or
29.
[0118] Referring now to FIG. 2a, and preceding Figures as needed,
there is seen one or more apparatus used for forming one or more
energy device structure. In one embodiment, in step 22, the
respective separate mixtures of dry particles formed in steps 19
and 20 are provided to respective containers 19 and 20. In one
embodiment, dry particles from container 19 are provided in a ratio
of about 1 gram to about 100 grams for every 1000 grams of dry
particles provided by container 20. The containers are positioned
above a device 41 of a variety used by those skilled in the art to
compact and/or calender materials into sheets. The compacting
and/or calendering function provided by device 41 can be achieved
by a roll-mill, calender, a belt press, a flat plate press, and the
like, as well as others known to those skilled in the art. Thus,
although shown in a particular configuration, those skilled in the
art will understand that variations and other embodiments of device
41 could be provided to achieve one or more of the benefits and
advantages described herein, which should be limited only by the
claims that follow.
[0119] Referring now to FIG. 2b, and preceding Figures as needed,
there is seen an apparatus used for forming one or more electrode
structure. As shown in FIG. 2b, the dry particles in containers 19
and 20 are fed as free flowing dry particles to a high-pressure nip
of a roll-mill 32. As they are fed towards the nip, the separate
streams of dry particles become intermixed and begin to loose their
freedom of motion. It is identified that use of relatively small
particles in one or more of the embodiments disclosed herein
enables that good particle mixing and high packing densities can be
achieved and that a concomitant lower resistivity may be achieved
as a result. The degree of intermixing can be to an extent
determined by process requirements and accordingly made
adjustments. For example, a separating blade 35 can be adjusted in
both a vertical and/or a horizontal direction to change a degree of
desired intermixing between the streams of dry particles. The speed
of rotation of each roll may be different or the same as determined
by process requirements. A resulting intermixed compacted dry film
34 exits from the roll-mill 32 and is self-supporting after only
one compacting pass through the roll-mill 32. The ability to
provide a self supporting film in one pass eliminates numerous
folding steps and multiple compacting/calendering steps that in
prior art embodiments are used to strengthen films to give them the
tensile strength needed for subsequent handling and processing.
Because the intermixed dry film 34 can be sufficiently self
supporting after one pass through roll-mill 32, it can easily and
quickly be formed into one long integral continuous sheet, which
can be rolled for subsequent use in a commercial scale manufacture
process. The dry film 34 can be formed as a self-supporting sheet
that is limited in length only by the capacity of the rewinding
equipment. In one embodiment, the dry film is between 0.1 and 5000
meters long. Compared to some prior art additive based films which
are described as non-self supporting and/or small finite area
films, the dry self-supporting films described herein are more
economically suited for large scale commercial manufacture.
[0120] Referring now to FIG. 2c, and preceding Figures as needed,
there is seen a diagram representing the degree of intermixing that
occurs between particles from containers 19 and 20. In FIG. 2c, a
cross section of intermixed dry particles at the point of
application to the high-pressure nip of roll-mill 32 is
represented, with "T" being an overall thickness of the intermixed
dry film 34 at a point of exit from the high-pressure nip. The
curve in FIG. 2c represents the relative concentration/amount of a
particular dry particle at a given thickness of the dry film 34, as
measured from a right side of the dry film 34 in FIG. 2b (y-axis
thickness is thickness of film, and x-axis is relative
concentration/amount of a particular dry particle). For example, at
a given thickness measured from the right side of the dry film 34,
the amount of a type of dry particle from container 19 (as a
percentage of the total intermixed dry particles that generally
exists at a particular thickness) can be represented by an X-axis
value "I". As illustrated, at a zero thickness of the dry film 34
(represented at zero height along the Y-axis), the percentage of
dry binder particles "I" from container 19 will be at a maximum,
and at a thickness approaching "T", the percentage of dry particles
from container 19 will approach zero.
[0121] Referring now to FIG. 2d, and preceding Figures as needed,
there is seen a diagram illustrating a distribution of the sizes of
dry binder and carbon particles. In one embodiment, the size
distribution of dry binder and carbon particles provided by
container 19 may be represented by a curve with a centralized peak,
with the peak of the curve representing a peak quantity of dry
particles with a particular particle size, and the sides of the
peak representing lesser amounts of dry particles with lesser and
greater particle sizes. In dry compacting/calendering step 24, the
intermixed dry particles provided by step 22 are compacted by the
roll-mill 32 to form the dry film 34 into an intermixed dry film.
In one embodiment, the dry particles from container 19 are
intermixed within a particular thickness of the resulting dry film
34 such that at any given distance within the thickness, the size
distribution of the dry particles 19 is the same or similar to that
existing prior to application of the dry particles to the roll-mill
32 (i.e. as illustrated by FIG. 2d). A similar type of intermixing
of the dry particles from container 20 also occurs within the dry
film 34 (not shown).
[0122] In one embodiment, the process described by FIGS. 2a-d is
performed at an operating temperature, wherein the temperature can
vary according to the type of dry binder selected for use in steps
16 and 23, but such that the temperature is less than the melting
point of the dry binder 23 and/or is sufficient to soften the dry
binder 16. In one embodiment, it is identified that when dry binder
particles 23 with a melting point of 150 degrees are used in step
23, the operating temperature at the roll-mill 32 is about 100
degrees centigrade. In other embodiments, the dry binder in step 23
may be selected to comprise a melting point that varies within a
range of about 50 degrees centigrade and about 350 degrees
centigrade, with appropriate changes made to the operating
temperature at the nip.
[0123] The resulting dry film 34 can be separated from the
roll-mill 32 using a doctor blade, or the edge of a thin strip of
plastic or other separation material, including metal or paper.
Once the leading edge of the dry film 34 is removed from the nip,
the weight of the self-supporting dry film and film tension can act
to separate the remaining exiting dry film 34 from the roll-mill
32. The self-supporting dry film 34 can be fed through a tension
control system 36 into a calender 38. The calender 38 may further
compact and densify the dry film 34. Additional calendering steps
can be used to further reduce the dry film's thickness and to
increase tensile strength. In one embodiment, dry film 34 comprises
a calendered density of about 0.50 to 0.70 gm/cm.sup.2.
[0124] Referring now to FIGS. 2e-f, there are seen carbon particles
encapsulated by dissolved binder of the prior art, and dry carbon
particles attached to dry binder of the present invention,
respectively. In the prior art, capillary type forces caused by the
presence of solvents diffuse dissolved binder particles in a wet
slurry based adhesive/binder layer into an attached additive-based
electrode film layer. In the prior art, carbon particles within the
electrode layer become completely encapsulated by the diffused
dissolved binder, which when dried couples the adhesive/binder and
electrode film layers together. Subsequent drying of the solvent
results in an interface between the two layers whereat carbon
particles within the electrode layer are prevented by the
encapsulating binder from conducting, thereby undesirably causing
an increased interfacial resistance. In the prior art, the extent
to which binder particles from the adhesive/binder layer are
present within the electrode film layer becomes limited by the size
of the particles comprising each layer, for example, as when
relatively large particles comprising the wet adhesive/binder layer
are blocked from diffusing into tightly compacted particles of the
attached additive-based electrode film layer.
[0125] In contrast to the prior art, particles from containers 19
and 20 are become intermixed within dry film 34 such that each can
be identified to exist within a thickness "T" of the dry film with
a particular concentration gradient. One concentration gradient
associated with particles from container 19 is at a maximum at the
right side of the intermixed dry film 34 and decreases when
measured towards the left side of the intermixed dry film 34, and a
second concentration gradient associated with particles from
container 20 is at a maximum at the left side of the intermixed dry
film 34 and decreases when measured towards the right side of the
intermixed dry film 34. The opposing gradients of particles
provided by container 19 and 20 overlap such that functionality
provided by separate layers of the prior art may be provided by one
dry film 34 of the present invention. In one embodiment, a gradient
associated with particles from container 20 provides functionality
similar to that of a separate prior art additive based electrode
film layer, and the gradient associated with particles from
container 19 provides functionality similar to that of a separate
prior art additive based adhesive/binder layer. The present
invention enables that equal distributions of all particle sizes
can be smoothly intermixed (i.e. form a smooth gradient) within the
intermixed dry film 34. It is understood that with appropriate
adjustments to blade 35, the gradient of dry particles 19 within
the dry film 34 can be made to penetrate across the entire
thickness of the dry film, or to penetrate to only within a certain
thickness of the dry film. In one embodiment, the penetration of
the gradient of dry particles 19 is about 5 to 15 microns. In part,
due to the gradient of dry particles 19 that can be created within
dry film 34 by the aforementioned intermixing, it is identified
that a lesser amount of dry particles need be utilized to provide a
surface of the dry film with a particular adhesive property, than
if dry particles 19 and dry particles 20 were pre-mixed throughout
the dry film.
[0126] In the prior art, subsequent application of electrolyte to
an additive based two-layer adhesive/binder and electrode film
combination may cause the binder, additive residues, and impurities
within the layers to dissolve and, thus, the two-layers to
eventually degrade and/or delaminate. In contrast, because the
binder particles of the present invention are distributed evenly
within the dry film according to their gradient, and/or because no
additives are used, and/or because the binder particles may be
selected to be substantially impervious, insoluble, and/or inert to
a wide class of additives and/or electrolyte, such destructive
delamination and degradation can be substantially reduced or
eliminated.
[0127] The present invention provides one intermixed dry film 34
such that the smooth transitions of the overlapping gradients of
intermixed particles provided by containers 19 and 20 allow that
minimized interfacial resistance is created. Because the dry binder
particles 23 are not subject to and/or do not dissolve during
intermixing, they do not completely encapsulate particles 12, 14,
and 21. Rather, as shown in FIG. 2f, after compacting, and/or
calendaring, and/or heating steps, dry binder particles 23 become
softened sufficiently such that they attach themselves to particles
12, 14, and 21. Because the dry binder particles 23 are not
completely dissolved as occurs in the prior art, the particles 23
become attached in a manner that leaves a certain amount of surface
area of the particles 12, 14, and 21 exposed; an exposed surface
area of a dry conductive particle can therefore make direct contact
with surface areas of other conductive particles. Because direct
conductive particle-to-particle contact is not substantially
impeded by use of dry binder particles 23, an improved interfacial
resistance over that of the prior art binder encapsulated
conductive particles can be achieved.
[0128] The intermixed dry film 34 also exhibits dissimilar and
asymmetric surface properties at opposing surfaces, which contrasts
to the prior art, wherein similar surface properties exist at
opposing sides of each of the separate adhesive/binder and
electrode layers. The asymmetric surface properties of dry film 34
may be used to facilitate improved bonding and electrical contact
to a subsequently used current collector (FIG. 3 below). For
example, when bonded to a current collector, the one dry film 34 of
the present invention introduces only one distinct interface
between the current collector and the dry film 34, which contrasts
to the prior art, wherein a distinct first interfacial resistance
boundary exists between a collector and additive based
adhesive/binder layer interface, and wherein a second distinct
interfacial resistance boundary exists between an additive-based
adhesive/binder layer and additive-based electrode layer
interface.
[0129] Referring now to FIG. 2g, and preceding Figures as needed,
there is seen one or more apparatus used for the manufacture of one
or more structure described herein. FIG. 2g illustrates apparatus
similar to that of FIG. 2a, except that container 19 is positioned
downstream from container 20. In one embodiment, in a step 29, the
dry particles provided by container 19 are fed towards a
high-pressure nip 38. By providing dry particles from steps 19 and
20 at two different points in a calender apparatus, it is
identified that the temperature at each step of the process may be
controlled to take into account different softening/melting points
of dry particles that may be provided by steps 19 and 20.
[0130] In FIG. 2g, container 19 is disposed to provide dry
particles 19 onto a dry film 33. In FIG. 2g, container 20 comprises
dry particles 12, 14, and 16, which are dry fibrillized and
provided to container 20 in accordance with principles described
above. A dry free flowing mixture from container 20 may be
compacted to provide the dry film 33 to be self-supporting after
one pass through a compacting apparatus, for example roll-mill 32.
The self-supporting continuous dry film 33 can be stored and rolled
for later use as an energy device electrode film, or may be used in
combination with dry particles provided by container 19. For
example, as in FIG. 2g, dry adhesive/binder particles comprising a
free flowing mixture of dry conductive carbon 21 and dry binder 23
from container 19 may be fed towards dry film 33. In one
embodiment, scatter coating equipment similar to that used in
textile and non-woven fabric industries is contemplated for
dispersion of the dry particles onto dry film 33. In one
embodiment, the dry film 33 is formed from dry particles 12, 14, 16
as provided by container 20. The dry particles from container 19
may be compacted and/or calendared against and within the dry film
33 to form a subsequent dry film 34, wherein the dry particles are
embedded and intermixed within the dry film 34. Through choice of
location of containers 19 and 20, separating blade 35, powder
feed-rate, roll speed ratios, and/or surface of rolls, it is
identified that the interface between dry particles provided to
form a dry particle based electrode film may be appropriately
varied. An embedded/intermixed dry film 34 may be subsequently
attached to a collector or wound onto a storage roll 48 for
subsequent use.
[0131] Alternative means, methods, steps, and setups to those
disclosed herein are also within the scope of the present invention
and should be limited only by the appended claims or their
equivalents. For example, in one embodiment, instead of the self
supporting continuous dry film 33 described herein, a commercially
available prior art additive-based electrode film could be provided
for subsequent calendering together with dry particles provided by
the container 19 of FIG. 2g. Although a resulting two-layer film
made in this manner would be at least in part additive based, and
could undesirably interact with subsequently used electrolyte, such
a two-layer film would nevertheless not need to utilize, or be
subject to the limitations associated with, a prior art slurry
based adhesive/binder layer. In one embodiment, instead of the
continuous dry film 33 of FIG. 2g, a heated collector (not shown)
could be provided, against which dry particles from container 19
could calendered. Such a combination of collector and adhered dry
particles from container 19 could be stored and provided for later
attachment to a separately provided electrode layer, which with
appropriate apparatus could be heat calendered to attach the dry
binder 23 in dry particles provided by container 19 to the
collector.
[0132] Referring to FIG. 3, and preceding Figures as needed, there
is seen an apparatus used to bond a dry process based film to a
current collector. In step 28, a dry film 34 is bonded to a current
collector 50. In one embodiment, the current collector comprises an
etched or roughened aluminum sheet, foil, mesh, screen, porous
substrate, or the like. In one embodiment, the current collector
comprises a metal, for example, copper, aluminum, silver, gold, and
the like. In one embodiment, current collector comprises a
thickness of about 30 microns. Those skilled in the art will
recognize that if the electrochemical potential allows, other
metals could also be used as a collector 50.
[0133] In one embodiment, a current collector 50 and two dry
film(s) 34 are fed from storage rolls 48 into a heated roll-mill 52
such that the current collector 50 is positioned between two
self-supporting dry films 34. In one embodiment, the current
collector 50 may be pre-heated by a heater 79. The temperature of
the heated roll-mill 52 may be used to heat and soften the dry
binder 23 within the two intermixed dry films 34 such that good
adhesion of the dry films to the collector 50 is effectuated. In
one embodiment, a roll-mill 52 temperature of at the nip of the
roll is between 100.degree. C. and 300.degree. C. In one
embodiment, the nip pressure is selected between 50 pounds per
linear inch (PLI) and 1000 PLI. Each intermixed dry film 34 becomes
calendared and bonded to a side of the current collector 50. The
two dry intermixed films 34 are fed into the hot roll nip 52 from
storage roll(s) 48 in a manner that positions the peak of the
gradients formed by the dry particles from container 19 directly
against the current collector 50 (i.e. right side of a dry film 34
illustrated in FIG. 2b). After exiting the hot roll nip 52, it is
identified that the resulting calendared dry film and collector
product can be provided as a dry electrode 54 for use in an energy
storage device, for example, as a double-layer capacitor electrode.
In one embodiment, the dry electrode 54 can be S-wrapped over chill
rolls 56 to set the dry film 34 onto the collector 50. The
resulting dry electrode 54 can then be collected onto another
storage roll 58. Tension control systems 51 can also be employed by
the system shown in FIG. 3.
[0134] Other means, methods, and setups for bonding of films to a
current collector 50 can be used to form energy storage device
electrodes, which should be limited only by the claims. For
example, in one embodiment (not shown), a film comprised of a
combination of a prior art additive-based electrode layer and
embedded dry particles from a container 19 could be bonded to a
current collector 50.
[0135] Referring now to FIGS. 4a and 4b, and preceding Figures as
needed, there are seen structures of an energy storage device. In
FIG. 4a, there are shown cross-sections of four intermixed dry
films 34, which are bonded to a respective current collector 50
according to one or more embodiments described previously herein.
First surfaces of each of the dry films 34 are coupled to a
respective current collector 50 in a configuration that is shown as
a top dry electrode 54 and a bottom dry electrode 54. According to
one or more of the embodiments discussed previously herein, the top
and bottom dry electrodes 54 are formed from a blend of dry
particles without use of any additives. In one embodiment, the top
and bottom dry electrodes 54 are separated by a separator 70. In
one embodiment, separator 70 comprises a porous paper sheet of
about 30 microns in thickness. Extending ends of respective current
collectors 50 are used to provide a point at which electrical
contact can be effectuated. In one embodiment, the two dry
electrodes 54 and separators 70 are subsequently rolled together in
an offset manner that allows an exposed end of a respective
collector 50 of the top electrode 54 to extend in one direction and
an exposed end of a collector 50 of the bottom electrode 54 to
extend in a second direction. The resulting geometry is known to
those skilled in the art as a jellyroll and is illustrated in a top
view by FIG. 4b.
[0136] Referring now to FIG. 4b, and preceding Figures as needed,
first and second dry electrodes 54, and separator 70, are rolled
about a central axis to form a rolled energy storage device
electrode 200. In one embodiment, the electrode 20 comprises two
dry films 34, each dry film comprising a width and a length. In one
embodiment, one square meter of a 150 micron thick dry film 34
weighs about 0.1 kilogram. In one embodiment, the dry films 34
comprise a thickness of about 80 to 260 microns. In one embodiment,
a width of the dry films comprises between about 10 to 300 mm. In
one embodiment, a length is about 0.1 to 5000 meters and the width
is between 30 and 150 mm. Other particular dimensions may be may be
determined by a required final energy storage device storage
parameter. In one embodiment, the storage parameter includes values
between 1 and 5000 Farads. With appropriate changes and
adjustments, other dry film 34 dimensions and other capacitance are
within the scope of the invention. Those skilled in the art will
understand that offset exposed current collectors 50 (shown in FIG.
4a) extend from the roll, such that one collector extends from one
end of the roll in one direction and another collector extends from
an end of the roll in another direction. In one embodiment, the
collectors 50 may be used to make electric contact with internal
opposing ends of a sealed housing, which can include corresponding
external terminals at each opposing end for completing an
electrical contact.
[0137] Referring now to FIG. 5, and preceding Figures as needed,
during manufacture, a rolled electrode 1200 made according to one
or more of the embodiments disclosed herein is inserted into an
open end of a housing 2000. An insulator (not shown) is placed
along a top periphery of the housing 2000 at the open end, and a
cover 2002 is placed on the insulator. During manufacture, the
housing 2000, insulator, and cover 2002 may be mechanically curled
together to form a tight fit around the periphery of the now sealed
end of the housing, which after the curling process is electrically
insulated from the cover by the insulator. When disposed in the
housing 2000, respective exposed collector extensions 1202 of
electrode 1200 make internal contact with the bottom end of the
housing 2000 and the cover 2002. In one embodiment, external
surfaces of the housing 2000 or cover 2002 may include or be
coupled to standardized connections/connectors/terminals to
facilitate electrical connection to the rolled electrode 1200
within the housing 2000. Contact between respective collector
extensions 1202 and the internal surfaces of the housing 2000 and
the cover 2002 may be enhanced by welding, soldering, brazing,
conductive adhesive, or the like. In one embodiment, a welding
process may be applied to the housing and cover by an externally
applied laser welding process. In one embodiment, the housing 2000,
cover 2002, and collector extensions 1202 comprise substantially
the same metal, for example, aluminum. An electrolyte can be added
through a filling/sealing port (not shown) to the sealed housing
1200. In one embodiment, the electrolyte is 1.5 M
tetramethylammonium or tetrafluoroborate in acetonitrile solvent.
After impregnation and sealing, a finished product is thus made
ready for commercial-sale and subsequent use.
[0138] Although the particular systems and methods herein shown and
described in detail are capable of attaining the above described
objects of the invention, it is understood that the description and
drawings presented herein represent some, but not all, embodiments
that are broadly contemplated. Structures and methods that are
disclosed may thus comprise configurations, variations, and
dimensions other than those disclosed. For example, other classes
of energy storage devices that utilize electrodes and adhesives as
described herein are within the scope of the present invention.
Also, different housings may comprise coin-cell type, clamshell
type, prismatic, cylindrical type geometries, as well as others as
are known to those skilled in the art. For a particular type of
housing, it is understood that appropriate changes to electrode
geometry may be required, but that such changes would be within the
scope of those skilled in the art. It is also contemplated that an
energy storage device made according to dry principles described
herein may comprise two different electrode films that differ in
compositions and/or dimensions (i.e. asymmetric electrodes).
Additionally, it is contemplated that principles disclosed herein
could be utilized in combination with a carbon cloth type
electrode. Thus, the scope of the present invention fully
encompasses other embodiments that may become obvious to those
skilled in the art and that the scope of the present invention is
accordingly limited by nothing other than the appended claims and
their equivalents.
* * * * *