U.S. patent application number 14/674035 was filed with the patent office on 2015-07-23 for metal fluoride and phosphate nanocomposites as electrode materials.
This patent application is currently assigned to RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY. The applicant listed for this patent is RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY. Invention is credited to Glenn Amatucci, Fadwa Badway.
Application Number | 20150207140 14/674035 |
Document ID | / |
Family ID | 39674822 |
Filed Date | 2015-07-23 |
United States Patent
Application |
20150207140 |
Kind Code |
A1 |
Amatucci; Glenn ; et
al. |
July 23, 2015 |
METAL FLUORIDE AND PHOSPHATE NANOCOMPOSITES AS ELECTRODE
MATERIALS
Abstract
The present invention relates to primary and secondary
electrochemical energy storage systems. More particularly, the
present invention relates to such systems as battery cells,
especially battery cells utilizing metal fluorides with the
presence of phosphates or fluorophosphates, which use materials
that take up and release ions as a means of storing and supplying
electrical energy.
Inventors: |
Amatucci; Glenn; (Peapack,
NJ) ; Badway; Fadwa; (Old Bridge, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY |
New Brunswick |
NJ |
US |
|
|
Assignee: |
RUTGERS, THE STATE UNIVERSITY OF
NEW JERSEY
New Brunswick
NJ
|
Family ID: |
39674822 |
Appl. No.: |
14/674035 |
Filed: |
March 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13943513 |
Jul 16, 2013 |
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14674035 |
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12025662 |
Feb 4, 2008 |
8518604 |
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13943513 |
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60899105 |
Feb 2, 2007 |
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Current U.S.
Class: |
429/219 ;
429/218.1; 429/220; 429/221; 429/223; 429/224; 429/231.95 |
Current CPC
Class: |
H01M 4/5805 20130101;
H01M 4/624 20130101; H01M 4/625 20130101; H01M 4/5825 20130101;
H01M 4/50 20130101; H01M 4/54 20130101; H01M 2300/0065 20130101;
H01M 6/18 20130101; Y02P 70/50 20151101; H01M 4/582 20130101; H01M
2004/021 20130101; H01M 4/52 20130101; Y02E 60/10 20130101; H01M
10/0525 20130101; H01M 2004/028 20130101; H01M 4/364 20130101 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 4/54 20060101 H01M004/54; H01M 6/18 20060101
H01M006/18; H01M 4/58 20060101 H01M004/58; H01M 4/62 20060101
H01M004/62 |
Claims
1. A battery cell comprising: (a) a positive electrode comprising a
nanocomposite; and (b) a solid electrolyte, wherein the positive
electrode is characterized by a specific capacity of about 100
mAh/g to 600 mAh/g at a voltage of about 2 volts to about 4 volts
when measured against a Li/Li+ reference potential, wherein the
nanocomposite comprises a metal fluoride component and a conductive
matrix, wherein the metal fluoride component is characterized by a
particle size about 1 nm to about 100 nm, wherein the metal
fluoride component is selected from the group consisting of CuF2,
BiF3, CoF3, AgF, MnF3, NiF2, and FeF3, and wherein the conductive
matrix comprises sulfur.
2. The battery cell according to claim 1, wherein the conductive
matrix is from about 5% to about 50% weight of the
nanocomposite.
3. The battery cell according to claim 1, wherein the nanocomposite
is x-ray amorphous.
4. The battery cell according to claim 1, wherein the conductive
matrix comprises intercalation compounds.
5. The battery cell according to claim 1, wherein the metal
fluoride component is FeF3.
6. The battery cell according to claim 1, wherein the nanocomposite
further comprises carbon or oxygen.
7. The battery cell according to claim 1, further comprising a
negative electrode, wherein the negative electrode comprises
lithium.
8. The battery cell according to claim 1, wherein the positive
electrode is rechargeable.
9. An electrochemical cell comprising: (a) a positive electrode
comprising a nanocomposite; (b) a negative electrode comprising
lithium; and (c) a separator disposed between the negative
electrode and positive electrode, wherein the positive electrode is
characterized by a specific capacity of about 100 mAh/g to 600
mAh/g at a voltage of about 2 volts to about 4 volts when compared
to a Li/Li+ reference potential, wherein the nanocomposite
comprises a metal fluoride component and a conductive matrix,
wherein the metal fluoride component is characterized by a particle
size about 1 nm to about 100 nm, and wherein the conductive matrix
comprises a sulfur material.
10. The electrochemical cell according to claim 9, wherein the
metal fluoride component is FeF3.
11. The electrochemical cell according to claim 9, wherein the
separator comprises a solid electrolyte.
12. The electrochemical cell according to claim 9, wherein the
positive electrode further comprises sulfur.
13. An electrochemical cell comprising: (a) a positive electrode
comprising a nanocomposite; (b) a negative electrode, the negative
electrode comprising lithium; and (c) a solid electrolyte, wherein
the positive electrode being characterized by a specific capacity
of about 100 mAh/g to 600 mAh/g at a voltage of about 2 volts to
about 4 volts when compared to a Li/Li+ reference potential,
wherein the nanocomposite comprises an iron fluoride component and
a conductive matrix, wherein the iron fluoride component is
characterized by a particle size about 1 nm to about 100 nm, and
wherein the conductive matrix comprises sulfur.
14. The electrochemical cell according to claim 13, wherein the
nanocomposite further comprises phosphate.
15. The electrochemical cell according to claim 13, wherein the
nanocomposite is characterized by a particle exhibiting an X-ray
diffraction (XRD) distribution into at least a first phase and a
second phase, wherein the first phase comprises the iron fluoride
component in the form of iron fluoride nanocrystallites.
16. The electrochemical cell according to claim 15, wherein the
second phase comprises an iron fluorophosphate.
17. The electrochemical cell according to claim 13, wherein the
nanocomposite is amorphous.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/943,513, filed Jul. 16, 2013, which is a
continuation of U.S. patent application Ser. No. 12/025,662, filed
Feb. 4, 2008, which matured into U.S. Pat. No. 8,518,604, issued
Aug. 27, 2013, which claims the benefit of U.S. Provisional Patent
Application No. 60/899,105, filed Feb. 2, 2007, the contents of all
of which are incorporated herein by reference in their
entirety.
FIELD OF INVENTION
[0002] The present invention relates to primary and secondary
electrochemical energy storage systems. More particularly, the
present invention relates to such systems as battery cells,
especially battery cells utilizing metal fluorides with the
presence of phosphates or fluorophosphates, which use materials
that take up and release ions as a means of storing and supplying
electrical energy.
BACKGROUND OF THE INVENTION
[0003] The lithium-ion battery cell is the premier high-energy
rechargeable energy storage technology of the present day.
Unfortunately, its high performance still falls short of energy
density goals in applications ranging from telecommunications to
biomedical. Although a number of factors within the cell contribute
to this performance parameter, the most crucial ones relate to how
much energy can be stored in the electrode materials of the cell.
Based on electrodes utilizing intercalation processes, the present
day state of the art Li-ion battery technology exhibits an energy
density in excess of 200 Wh/kg and 420 Wh/l. The energy density of
lithium battery technology is far less than half of the theoretical
energy densities that could be achieved. The technology is
currently limited by the energy density of the positive electrode.
This is due to intercalation reactions limiting the amount of
Li.sup.+ inserted, thereby limiting electron transfer to typically
less than 1e.sup.- per compound such as LiMeO.sub.2, where Me is a
transition metal.
[0004] During the course of development of rechargeable
electrochemical cells, such as lithium (Li) and lithium-ion battery
cells and the like, numerous materials capable of reversibly
accommodating lithium ions have been investigated. Materials of the
present invention include conversion and reverse conversion
compounds which allow for multiple electrons to be transferred to
the active electrode to reduce fully to the metal state plus
lithium salt and then subsequently reoxidize back to the original
compounds. Existing state of the art materials include occlusion
and intercalation materials, such as carbonaceous compounds,
layered transition metal oxide, and three dimensional pathway
spinels which have proven to be particularly well-suited to such
applications. However, even while performing reasonably well in
recycling electrical storage systems of significant capacity, many
of these materials exhibit detrimental properties, such as marginal
environmental compatibility and safety, which detract from the
ultimate acceptability of the rechargeable cells. In addition, some
of the more promising materials are available only at costs that
limit widespread use. However, of most importance is the fact that
the present state of the art materials have the capability to store
relatively low capacity of charge per weight of material (specific
capacity, mAh/g) or energy per weight (specific energy, Wh/kg).
[0005] Materials of choice in the fabrication of rechargeable
battery cells, particularly highly desirable and broadly
implemented Li-ion cells, have for some considerable time centered
upon graphitic negative electrode compositions, which provide
respectable capacity levels in the range of 300 mAh/g.
Complementary positive electrode materials in present cells use
less effective layered intercalation compounds, such as
LiCoO.sub.2, which generally provides capacities in the range of
150 mAh/g. Alternative intercalation materials, such as
LiNiO.sub.2, and LiMn.sub.2O.sub.4, have more recently gained favor
in the industry, since, although exhibiting no appreciable increase
in specific capacity, these compounds are available at lower cost
and provide a greater margin of environmental acceptability.
[0006] Due to increasing demand for ever more compact electrical
energy storage and delivery systems for all manner of advancing
technologies, the search continues for battery cell materials
capable of, on the one hand, providing greater specific capacity
over wider ranges of cycling rates, voltages, and operating
temperatures, while, on the other hand, presenting fewer
environmental hazards and greater availability at lower processing
and fabrication costs.
[0007] In the search of material systems which can deliver much
higher specific capacities and energy, interest has shifted to
examination of the more active fluoride compounds. Primary metal
fluorides have been known for well over 30 years as attractive
electrode materials, however, the higher voltage materials exhibit
a high bandgap resulting in insulator properties and very poor
electrochemical activity. Recently, reversible conversion reactions
in metal fluorides have been shown to occur. Badway et al. (Journal
of The Electrochemical Society, 150(9) A1209-A1218 (2003)) reported
the use of carbon metal fluoride nanocomposites to enable the
electrochemical activity of metal fluorides. Their studies have
shown that reducing the particle size of high bandgap, insulating
metal fluorides to the nanodimensions in combination with highly
conductive carbon resulted in the enablement of a new metal
fluoride conversion process resulting in a major improvement in
specific capacity relative to current state of the art. Badway et
al. reported greater than 90% recovery of the FeF.sub.3 theoretical
capacity (less than 600 mAh/g) in the 4.5-1.5 V region through
reversible conversion, which is a fundamentally different energy
storage mechanism compared with the present state of the art
intercalation.
[0008] Until recently, full utilization of certain metal fluorides,
such as copper fluoride, has not been realized. Researchers have
tried to enable this high energy density compound for more than 30
years with only limited success because of poor utilization of the
material. Copper fluoride has a theoretical conversion potential of
approximately 3.2V and a discharge specific capacity of
approximately 520 mAh/g. This leads to an exceptionally high energy
density in excess of 1500 Wh/kg. Such capacity values are over 300%
higher than those attained in present day state-of-the-art
rechargeable Li battery cells based on LiCoO.sub.2 intercalation
compounds. With respect to existing primary cathode compounds,
copper fluoride would exceed the widely utilized MnO.sub.2 energy
density by almost a factor of two and copper fluoride compounds
exceed the volumetric energy density of copper monofluoride by
20-30%. U.S. Patent Publication No. 2006/0019163, which is hereby
incorporated by reference discusses nanocomposite technology that
has enabled greater than 99% of the theoretical specific capacity
of copper fluoride.
[0009] Despite the promising energy densities extracted for a
number of the metal fluoride nanocomposite technologies, challenges
still exist. For the reversible conversion metal fluorides, the
ability to retain a larger percentage of the capacity during
reversible cycling is desired. In copper fluoride nanocomposites,
the material has a poor ability to retain charge when stored at
elevated temperatures in its partially discharged state. For
example, state of the art materials typically lose 100% of their
capacity after one week at 40.degree. C. or 60.degree. C. when they
are previously partially discharged. These present a great
challenge to researchers where no obvious methodology exists to
improve such performances.
[0010] Hence, there is a need in the art for electrical
energy-storage and delivery systems that utilize copper fluoride
effectively.
SUMMARY OF THE INVENTION
[0011] The present invention relates generally to the formation and
utilization of nanostructures of metal fluorides. More preferably,
the invention relates to the formation of metal fluoride
nanostructures which incorporate novel conducting matrices and are
in the presence of phosphates or fluorophosphates. The
nanostructures serve as active electrode component materials for
use in electrochemical cells, such as lithium battery cells,
capable of exhibiting high specific capacity at high recharge
and/or discharge reates.
[0012] The invention relates, more specifically, to the formation
of metal fluoride based nanocomposites with the presence of
phosphates or fluorophosphates. An aspect of the invention relates
to the improvement of the electrochemical properties of metal
fluoride nanocomposites with the addition of phosphate or
fluorophosphate species to the composite.
[0013] Another embodiment of the present invention provides a
composition including a metal fluoride nanocomposite compound with
a phosphate or fluorophosphate species as an electrode material for
an electrochemical storage unit.
[0014] In a further embodiment of the present invention, a method
of preparing a metal fluoride nanocomposite compound comprises the
steps of combining a metal fluoride and a conductive matrix to form
a first product, combining the first product and a phosphate adding
group, and fabricating the second product into a nanocomposite.
Specifically, the phosphate adding group may be lithium
metaphosphates, lithium hydrogen phosphates, methyl phosphates,
ammonium phosphates, hydrogen phosphates, or various metal
phosphates.
[0015] In a further embodiment, the invention is drawn to a
composite comprising at least about 50% molar content of a metal
fluoride and a phosphate.
[0016] In a further embodiment, the composite demonstrates a
specific capacity of about 100 mAh/g to about 600 mAh/g at a
voltage of about 2 volts to about 4 volts when compared to a
Li/Li.sup.+ reference potential.
[0017] In a further embodiment, the metal of the metal fluoride is
selected from the group consisting of Fe, Cr, Nb, Rh, Ag, Au, Se,
Co, Te, Ni, Mn, Cu, V, Mo, Pb, Sb, Bi, or Si. Preferably, the metal
is selected from the group consisting Cu, Bi, or Fe.
[0018] In another embodiment, the metal fluoride is CuF.sub.2.
[0019] In another embodiment, the metal fluoride is BiF.sub.3.
[0020] In yet another embodiment, the metal fluoride is doped with,
that is, injected with or annealed with oxygen by abstracting
oxygen from another component in the nanocomposite, up to
approximately 10% oxygen.
[0021] In another embodiment of the present invention, the
phosphate is present in an amount that is less than 50 weight % of
the composition.
[0022] In still a further embodiment, the phosphate is a distinct
subdomain distributed within the composite.
[0023] In another embodiment, the phosphate is a metal phosphate,
fluorophosphate, metal fluorophosphate. Preferably the phosphate is
a copper fluorophosphate.
[0024] In an embodiment of the invention, the composite further
comprises a conductive matrix selected from the group consisting of
VO.sub.2, MoO.sub.2, MoO.sub.3, MoS.sub.2, V.sub.2O.sub.5,
V.sub.6O.sub.13, NiO, CuO, carbon fluorides, nitrides, selenide,
tellurides, silicates, molybdenum sulfides, molybdenum oxysulfides,
titanium sulfide, chromium oxide, manganese oxide (MnO.sub.2), and
MoO.sub.xF.sub.z, wherein x is 0.ltoreq.x.ltoreq.3 and z is
0.ltoreq.z.ltoreq.5 combined in such a way that an effective charge
on the Mo cation is not more than 6.sup.+.
[0025] In another embodiment, the invention is drawn to a
nanocomposite comprising at least approximately 50% molar content
of a metal fluoride and a phosphate.
[0026] In another embodiment of the invention, the nanocomposite
comprises at least one dimension of each of the metal fluoride and
the phosphate, wherein each dimension is less than 100 nm.
[0027] In another embodiment of the invention, the nanocomposite
comprises at least two dimensions of each of the metal fluoride and
the phosphate, wherein each dimension is less than 100 nm.
[0028] In a further embodiment of the invention, the nanocomposite
composition is formed of crystallites of about 1 nm to about 100 nm
in diameter.
[0029] In an embodiment of the invention, the nanocomposite
demonstrates a specific capacity around 100 mAh/g to about 600
mAh/g at a voltage of about 2 volts to about 4 volts when compared
to a Li/Li.sup.+ reference potential.
[0030] In another embodiment of the invention, the phosphate is a
distinct nanodomain distributed within the composite.
[0031] In an embodiment of the invention, a nanocomposite further
comprises a conductive matrix selected from the group consisting of
VO.sub.2, MoO.sub.2, MoO.sub.3, MoS.sub.2, V.sub.2O.sub.5,
V.sub.6O.sub.13, NiO, CuO, carbon fluorides, nitrides, selenides,
tellurides, silicates, molybdenum sulfides, molybdenum oxysulfides,
titanium sulfide, chromium oxide, manganese oxide (MnO.sub.2), and
MoO.sub.xF.sub.z, wherein x is 0.ltoreq.x.ltoreq.3 and z is
0.ltoreq.z.ltoreq.5 combined in such a way that an effective charge
on the Mo cation is not more than 6.sup.+.
[0032] In a further embodiment of the invention, the nanocomposite
further comprises carbon or oxygen.
[0033] In an embodiment of the invention, wherein the specific
capacity of the nanocomposite is rechargeable by passing a current
through the nanocomposite in a direction opposite a discharge
direction.
[0034] In yet another embodiment, the invention provides an
electrochemical cell comprising a negative electrode, a positive
electrode comprising a nanocomposite comprising a metal fluoride
and a phosphate, and a separator disposed between the negative and
positive electrodes.
[0035] In an embodiment, the cell further comprises an electrolyte
composition, which includes at least one metallic salt. The at
least one metallic salt is selected from the group consisting of a
lithium salt, a magnesium salt, a calcium salt, a zinc salt, a
manganese salt, and a yttrium salt.
[0036] In an embodiment, the cell has a specific capacity, the
specific capacity rechargeable by passing a current through the
nanocomposite in a direction opposite a discharge direction.
[0037] In another embodiment, the nanocomposite is formed of
particles that are about 1 nm to about 100 nm in diameter.
[0038] In yet another embodiment, the cell utilizes a lithium-based
negative electrode.
[0039] In another embodiment, the cell further comprising a
negative electrode selected from the group consisting of a
magnesium-based negative electrode, a calcium-based negative
electrode, a zinc-based negative electrode, a manganese-based
negative electrode, and a yttrium-based negative electrode.
[0040] In an embodiment, the invention provides a method of
preparing a nanocomposite comprising a metal fluoride and a
phosphate, the method comprising the steps of combining a metal
fluoride and a conductive matrix forming a first product, combining
said first product with a phosphate-adding group forming a second
product, and fabricating the second product into a
nanocomposite.
[0041] In an embodiment, the method further comprises the step of
milling the copper fluoride and conductive matrix by high energy
milling.
[0042] In another embodiment, the method of the invention further
comprises milling the first product and the phosphate adding
compound by high energy milling.
[0043] In an embodiment of the invention, the conductive matrix is
selected from the group consisting of VO.sub.2, MoO.sub.2,
MoO.sub.3, MoS.sub.2, V.sub.2O.sub.5, V.sub.6O.sub.13, NiO, CuO,
Bi.sub.2Te.sub.3, carbon fluorides, nitrides, selenides,
tellurides, silicates, molybdenum sulfides, molybdenum oxysulfides,
titanium sulfide, chromium oxide, manganese oxide (MnO.sub.2), and
MoO.sub.xF.sub.z, wherein x is 0.ltoreq.x.ltoreq.3 and z is
0.ltoreq.z.ltoreq.5 combined in such a way that an effective charge
on the Mo cation is not more than 6.sup.+. Preferably, the
conductive matrix is MoO.sub.3, MoS.sub.2, or Bi.sub.2Te.sub.3.
[0044] In an embodiment of the invention, the phosphate adding
group is lithium metaphosphate, lithium hydrogen phosphate,
hydrogen phosphate, methyl phosphate, ammonium phosphate or
ammonium hydrogen phosphate. Preferably, the phosphate adding group
is present in an amount that is less than 50 weight % of the
composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a schematic depicting charge transport issues
relative to a metal fluoride nanocomposite containing a mixed
conducting matrix;
[0046] FIG. 2 is a graph depicting voltage as a function of
specific capacity of a copper fluoride compound and phosphate
nanocomposite where varying weight percentages of lithium
metaphosphate were mixed with the composition;
[0047] FIG. 3 shows X-ray diffraction data of copper fluoride
compound and phosphate nanocomposite compounds fabricated with
varying weight percentages of lithium metaphosphate;
[0048] FIG. 4 is a graph depicting voltage as a function of
specific capacity for a copper fluoride compound and phosphate
nanocomposite where varying weight percentages of lithium
metaphosphate were added and subsequently annealed at varying
temperatures and times;
[0049] FIG. 5 depicts X-ray diffraction data of copper fluoride
compound and phosphate nanocomposites where lithium metaphosphate
was added and subsequently annealed at varying temperatures and
times;
[0050] FIG. 6 is a graph depicting voltage as a function of
specific capacity for a copper fluoride compound and phosphate
nanocomposite where varying weight percentages of lithium
dihydrogen phosphate were added;
[0051] FIG. 7 depicts X-ray diffraction data of copper fluoride
compound and phosphate nanocomposites fabricated with varying
weight percentages of lithium dihydrogen phosphate;
[0052] FIG. 8 is a graph depicting voltage as a function of
specific capacity for copper fluoride compound and phosphate
nanocomposites where varying weight percentages of hydrogen
phosphate were added;
[0053] FIG. 9 depicts X-ray diffraction data of copper fluoride
compound and phosphate nanocomposites fabricated with varying
weight percentages of hydrogen phosphate;
[0054] FIG. 10 is a graph depicting specific capacity as a function
of cycle number of a bismuth fluoride compound and phosphate
nanocomposite where varying amounts of lithium metaphosphate were
added; and
[0055] FIG. 11 is a graph depicting voltage as a function of
specific capacity for a copper fluoride compound incorporating
bismuth telluride as a conductive matrix where lithium hydrogen
phosphate has been added.
DETAILED DESCRIPTION OF THE INVENTION
[0056] The present invention provides improved materials for
battery components, specifically for positive electrodes in primary
and rechargeable cells. More particularly, the invention relates to
the improvement of the electrochemical properties of metal fluoride
nanocomposites with the addition of phosphate or fluorophosphate
species to the composite.
[0057] In one embodiment, the present invention provides a
composite comprising a metal fluoride and a phosphate, wherein the
phosphate may be a distinct subdomain of the composite or
alternatively, is part of the metal fluoride. The composite
demonstrates a specific capacity of from about 100 mAh/g to from
about 600 mAh/g at a voltage of about 2 V to about 4 V when
compared to a Li/Li.sup.+ reference potential. In a preferred
embodiment, the demonstrated specific capacity is from about 300
mAh/g to about 500 mAh/g. As used herein, "specific capacity"
refers to the amount of energy the nanocomposite contains in
milliamp hours (mAh) per unit weight. In an embodiment, the metal
fluoride comprises at least 50% molar content of the composite.
[0058] In another embodiment, the present invention provides a
nanocomposite comprising a metal fluoride and a phosphate, wherein
the phosphate may be a distinct subdomain of the composite or
alternatively, is part of the metal fluoride. The nanocomposite
demonstrates specific capacity of from about 100 mAh/g to from
about 600 mAh/g at a voltage of about 2 V to about 4 V when
compared to a Li/Li.sup.+ reference potential. In a preferred
embodiment, the demonstrated specific capacity is from about 300
mAh/g to about 500 mAh/g.
[0059] The nanocomposite may be composed of a multitude of phases,
each with a distinct function. For example, exceptional performance
of metal fluoride compositions is enabled when the metal fluorides
are formed into nanocomposites with transport assisting materials.
The latter materials consist of carbons, metal oxides, metal
sulfides, metal nitrides, and combinations of these.
[0060] The metal fluoride of the composition includes a metal. One
of skill in the art can readily identify metals for use for use in
metal fluoride compound composites of the present invention. Such
metals include, but are not limited to, non-transition metals and
transition metals, preferably transition metals, and more
preferably first row transition metals. Specific examples of metals
for use in nanocomposites of the present invention include, but are
not limited to: V, Cr, Mn, Fe, Co, Ni Cu, Nb, Mo, Se, Rh, Te, Ag,
Au, Pb, Sb, and Bi.
[0061] In a preferred embodiment, the metal is Bi, Cu, or Fe.
Preferably, the metal fluoride of the invention is CuF.sub.2 or
BiF.sub.3. The metal fluoride of the present invention may be
further doped up with 10% oxygen.
[0062] The phrase, "nanocomposite" can be defined as a composite of
materials whose primary molar constituency is a metal fluoride
where all the components have at least one dimension, which is less
than 100 nm. Although the distribution of such nanocomposite is not
limited by definition, all components must be contained within an
area that is less than 1000 nm, preferably 200-800 nm.
[0063] In one embodiment, the specific capacity of the
nanocomposite is reversible. "Reversible specific capacity" means
that the nanocomposite of the present invention may be recharged by
passing a current through it in a direction opposite to that of
discharge.
[0064] The nanocomposite may be a "metal fluoride compound
nanocomposites," which, as used herein, means nanocrystallites
comprising at least a "metal fluoride compound" incorporated within
a nanocomposite, which may or may not be of nanoparticle size. As
used herein, the phrase, "metal fluoride compound" includes any
compound that comprises the elements of fluorine (F) a metal for
use in lithium fluoride compounds including, but not limited to,
Fe, Cr, Nb, Rh, Ag, Au, Co, Ni, Mn, Cu, V, Mo, Pb, Se, Sb, Te, Bi,
or Si. Examples of metal fluoride compounds include, but are not
limited to, CuF.sub.2 and BiF.sub.3.
[0065] The performance of the nanocomposites is greatly improved
with the addition of phosphate or fluorophosphate to the
nanocomposite structure. The phosphate species have been found to
improve the performance of the metal fluoride nanocomposites either
through becoming a distributed nanodomain within the composite or
inducing the formation of a metal phosphate or fluorophosphate with
the host metal of the metal fluoride. Such phosphates can be added
as, for example, lithium metaphosphates, lithium hydrogen
phosphates, methyl phosphates, ammonium phosphates, hydrogen
phosphates, or as various metal phosphates. Due to the extreme
reactivity at the nanodimensions, such phosphates may lose their
individual character and combine partially with the components of
the existing matrix to form mixed metal phosphate or metal
fluorophosphate. Such examples of the latter reaction are clearly
defined in the examples below in the case of copper
fluoride/molybdenum oxide nanocomposites, where the addition of
various phosphates induces the formation of a copper
fluorophosphate. In many cases, the identification of such phases
are extremely difficult through traditional techniques such as
x-ray diffraction, electron diffraction and vibrational analysis.
Such phases can then be considered to be x-ray amorphous. The
performance improvements derived from this invention range from
improved storage at elevated temperatures to retention of capacity
with cycling.
[0066] The phosphate may be a fluorophosphate, a metal phosphate,
or a metal fluorophosphate, wherein the metal is the same metal as
in the metal fluoride. In one embodiment, the phosphate is copper
phosphate. The nanocomposite of the present invention includes,
preferably, from about 2 to about 50 weight % of phosphates. In
another, preferred, embodiment, the nanocomposite of the present
invention includes from about 2 to about 25 weight % of phosphates.
The nanocomposites of the present invention may further include a
conductive matrix. As used herein, a "conductive matrix" refers to
a matrix that includes conductive materials, some of which may be
ionic and/or electronic conductors. Preferably the matrix will
retain both ionic and electronic conductivity; such materials are
commonly referred to as "mixed conductors".
[0067] The enablement of reversible conversion metal fluorides
relies on effective transport of both ions and electrons to the
metal fluoride nanodomain, as shown in FIG. 1. The electronic
charge is brought to the nanocomposite via the electronically
conductive carbon black typically utilized in the porous positive
electrode along with lithium ions through the ionically conductive
electrolyte. In order for a nanocomposite concept to be utilized
effectively, the electronic and ionic charge must be transported
from the carbon and electrolyte conductors through a highly
conducting matrix, which links all the metal fluoride nanodomains
within the nanocomposite. Initial matrices consisted of carbon but
recently mixed conducting matrices combine the ionic and electronic
transport duties to one material, the mixed conductor. Mixed
conductors utilized as the matrix can be easily represented by
intercalation compounds, which maintain excellent electronic and
ionic conduction. In order to exhibit the latter, the material
should intercalate and reduce at a voltage above or similar to the
conversion reaction of the metal fluoride. Attractive materials
such as V.sub.2O.sub.5, MoS.sub.2, and MoO.sub.3-6 can be utilized.
Examples of metal fluorides enabled by these MCM matrices are
nanocomposites of FeF.sub.3 (V.sub.2O.sub.5), BiF.sub.3
(MoS.sub.2), and CuF.sub.2 (MoO.sub.3), respectively. In all cases
the nanocomposites exhibit relative low surface areas as the
electronic and ionic charge are carried by the matrix to the
nanodomains.
[0068] Suitable conductive matrices include, but are not limited
to, sulfides, fluorides, silicates, selenides, tellurides,
nitrides, VO.sub.2, MoO.sub.2, MoS.sub.2, NiO, MoO.sub.3,
molybdenum sulfides, molybdenum oxysulfides, titanium sulfide,
MoO.sub.xF.sub.z, wherein x is 0.ltoreq.x.ltoreq.3 and z is
0.ltoreq.z.ltoreq.5 combined in such a way that the effective
charge on the Mo cation is not more than 6.sup.+, V.sub.2O.sub.5,
V.sub.6O.sub.13, CuO, MnO.sub.2, chromium oxides, and carbon
fluorides, for example, CF.sub.0.8.
[0069] The nanocomposite of the present invention includes,
preferably, from about 5 to about 50 weight % of a conductive
matrix. In another, preferred, embodiment, the metal fluoride of
the present invention includes from about 1 to about 25 weight % of
a conductive matrix. Even more preferably, the composite of the
present invention includes from about 2 to about 15 weight % of a
conductive matrix.
[0070] In another embodiment, the nanocomposite may further include
oxygen. One of skill in the art will recognize that oxygen can
substitute for fluorine in metal fluorides. Oxygen may act to
significantly improve the electrical conductivity of the
nanocomposite of the invention.
[0071] In another embodiment, the nanocomposite may include a
second metal.
[0072] In yet another embodiment, both oxygen and a second metal
are included in the nanocomposite of the present invention.
[0073] Carbon may, optionally, be included in the nanocomposite of
the present invention. Preferably, less than 50 weight % of carbon
is used. More preferably, less than 25 weight % carbon is used.
Even more preferably less than 5 weight % carbon is used. Yet,
still more preferably, the nanocomposite is of the formula
Cu.sub.xMe.sub.yF.sub.zO.sub.wC, wherein x+z>y+w and w>0, for
example, when copper is utilized.
[0074] The nanocomposites of the present invention may be prepared
by extreme, high impact-energy milling of a mixture that includes a
metal fluoride compound and 5 to 50 weight % of a conductive matrix
to form a first product. The first product containing a metal
fluoride and conductive matrix is then milled with 2-50 weight % of
one of lithium metaphosphate, lithium hydrogen phosphate, hydrogen
phosphate, methyl phosphate, ammonium phosphate, or ammonium
hydrogen phosphate to add a phosphate species to the nanocomposite.
Thus, the nanocomposite of the present invention can be prepared by
using an impact mixer/mill such as the commercially available SPEX
8000 device (SPEX Industries, Edison N.J., USA). Unlike the
shearing action of conventional planetary, roller, or ball mills,
which at best may allow for size reduction of crystallite particles
to the micrometer range, the extremely high-energy impact action
impressed upon the component mixture by the impact mill provides,
within milling periods as short as about 10 minutes, a particle
size reduction of the processed material to the nanostructure range
of less than about 100 nm. Further milling for as little as 30
minutes up to about 4 hours brings about crystallite-particle size
reduction to less than about 40 nm.
[0075] Alternatively a planetary milling apparatus (Retsch) may be
utilized to perform similar operations in ZrO.sub.2 lined cells.
For milling of phosphates, 2-50 weight % of phosphates are premixed
with the reagents before milling in a similar way to form the
desired nanocomposite. The cell was sealed before milling and
opened and the contents were removed after milling in the helium
atmosphere of the glovebox.
[0076] Other methods may be used to form the nanocomposites of the
present invention. As will be evident to a skilled artisan,
solution or gel techniques may be used to fabricate the
nanocomposites. Generally, as used herein, solution, gel, or
high-energy impact milling techniques are referred to as
"nanocomposite fabrication methods."
[0077] When a metal fluoride is milled with another component, the
metal fluoride undergoes chemical changes such that its X ray
diffraction characteristics takes on the character of a new, highly
electrochemically active material, although retaining major aspects
of the metal fluoride. In addition, the nanocrystallite formation
can be characterized easily by well-known methods such as Bragg
peak broadening in x-ray diffraction and microscopy by methods such
as transmission electron microscopy.
[0078] In another aspect of the present invention, an
electrochemical cell, preferably a primary or rechargeable battery
cell, is provided which employs the inventive nanocomposites as the
cathode material. The cell may be prepared by any known method. The
inventive nanocomposite electrode (cathode) materials function well
with most other known primary or secondary cell composition
components, including polymeric matrices and adjunct compounds, as
well as with commonly used separator and electrolyte solvents and
solutes.
[0079] The nanocomposite may be composed of a multitude of phases,
each with a distinct function. For example, exceptional performance
of metal fluoride compositions is enabled when the metal fluorides
are formed into nanocomposites with transport assisting materials.
The latter materials consist of carbons, metal oxides, metal
tellurides, metal sulfides, metal selenides, metal nitrides, and
combinations of these.
[0080] Electrolyte compositions commonly used in known rechargeable
electrochemical-cell fabrication serve well in the cells of the
present invention. These electrolyte compositions may include one
or more metallic salts, such as, but not limited to, lithium,
magnesium, calcium, zinc, manganese, and yttrium. Lithium salts,
such as LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, and the like,
dissolved in common cyclic and acyclic organic solvents, such as
ethylene carbonate, dimethyl carbonate, propylene carbonate, ethyl
methyl carbonate, and mixtures thereof, may be used. Another
electrolyte which may be used consists of lithium
bis(trifluoromethane sulfone imide (LiN(SO.sub.2CF.sub.3).sub.2
LiTFSI) salt dissolved in a blend of carbonate solvents. As with
optimization of the nanocomposites of the present invention,
specific combinations of electrolyte components will be a matter of
preference of the cell fabricator and may depend on an intended use
of the cell, although consideration may be given to the use of
solutes such as LiBF.sub.4, which appear less susceptible during
cell cycling to hydrolytically forming HF, which could affect the
optimum performance of some metal fluorides. For such reason, for
instance, a LiBF.sub.4:propylene carbonate electrolyte may be
preferred over one comprising a long-utilized standard solution of
LiPF.sub.6 in a mixture of ethylene carbonate:dimethyl carbonate.
In addition, such nanocomposites may be incorporated into solid
state polymer cells utilizing solid state ionically conducting
matrices derived from compounds such as polyethylene oxide (PEO).
Nanocomposites also may be fabricated by thin film deposition
techniques and be incorporated into solid state thin film lithium
batteries utilizing a glassy electrolyte. Finally, such electrode
materials may be incorporated into cells utilizing ionic liquid
solvents as the electrolytes.
[0081] Likewise, the negative electrode members of electrochemical
cells may advantageously include any of the widely used known ion
sources such as lithium metal and lithium alloys, such as those
comprised of lithium tin, lithium silicon, lithium aluminum,
lithiated carbons such as those based on coke, hard carbon,
graphite, nanotubes or C.sub.60, and lithiated metal nitrides. The
negative electrode members of electrochemical cells also may
further include either a magnesium-, calcium-, zinc-, manganese-,
or yttrium-based negative electrode.
[0082] In another aspect of the present invention, an
electrochemical cell, preferably a primary or rechargeable battery
cell, is provided which employs the nanocomposite of the present
invention as the cathode material. The cell may be prepared by any
known method. The nanocomposite electrode (cathode) materials
function well with most other known primary or secondary cell
composition components, including polymeric matrices and adjunct
compounds, as well as with commonly used separator and electrolyte
solvents and solutes.
[0083] In another aspect of the present invention, a nanocomposite
having capacity retention upon storage is prepared by a method
including the steps of (a) combining metal fluoride and a
conductive matrix to form a first product; (b) combining the first
product with a phosphate adding compound forming a second product
and (c) fabricating the second product a into a nanocomposite by
any suitable known method for forming nanocomposites. Preferably,
the method is the high-energy impact milling method described
above. Suitable phosphate adding compounds include lithium
metaphosphate, lithium hydrogen phosphate, hydrogen phosphate,
methyl phosphate, ammonium phosphate, or ammonium hydrogen
phosphate. A suitable conductive matrix may be one selected from
metal oxides, sulfides, selenides, tellurides, nitrides, or more
specifically, VO.sub.2, MoO.sub.2, MoS.sub.2, MoO.sub.3,
V.sub.2O.sub.2, CuO, CF.sub.0.8 and MoO.sub.xF.sub.z. Preferably,
the conductive matrix is MoO.sub.xF.sub.z, wherein x is
0.ltoreq.x.ltoreq.3 and z is 0.ltoreq.z.ltoreq.5 combined in such a
way that the effective charge on the Mo cation is not more than
6.sup.+ or MoO.sub.3.
[0084] The present invention is illustrated more fully by means of
the following non-limiting Examples which set forth the application
of phosphates to three types of metal fluoride nanocomposites. The
first nanocomposite consists of CuF.sub.2:MoO.sub.3 (a transition
metal fluoride and a metal oxide matrix), while the second
nanocomposite BiF.sub.3:MoS.sub.2 (a non-transition metal fluoride
and a metal sulfide matrix). A third nanocomposite consists of
CuF:Bi.sub.2Te.sub.3.
EXAMPLES
[0085] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how to make and use the present invention, and are
not intended to limit the scope of what the inventors regard as
their invention nor are they intended to represent that the
experiments below are all or the only experiments that were
performed. Efforts have been made to ensure accuracy with respect
to numbers used (e.g. amounts, temperature, etc.) but some
experimental errors and deviations should be accounted for. Unless
indicated otherwise, parts are parts by weight, molecular weight is
weight by average molecular weight, temperature is in degrees
Centigrade, and pressure is at or near atmospheric.
Example 1
Preparation of Copper Fluoride and Phosphate Nanocomposite with
MoO3 Conductive Matrix with Lithium Metaphosphate
[0086] Approximately 1 g CuF.sub.2, and 15% MoO.sub.3 were milled
in a high-energy impact mill under a helium atmosphere for 20 min.
and subsequently annealed at 200.degree. C. before the sample was
extracted. The resulting mixture is designated "CM" herein. CM was
composed of crystallites of approximately 30 nm. After fabrication
of CM, various weight percentages of lithium metaphosphate
(Li.sub.3PO.sub.3--LiH.sub.2PO.sub.4) were mixed with the CM
composition. Specifically, 2 weight % lithium metaphosphate; 5
weight % lithium metaphosphate, 10 weight % lithium metaphosphate;
15 weight % metaphosphate %; and 20 weight % lithium metaphosphate
were mixed with the CM in different samples. A nanocomposite was
formed by high energy milling of the composition for a period of 1
h, after which the composition was annealed at 250.degree. C. for a
period of 30 minutes in Argon. The compositions were fabricated
into electrodes and assembled into duplicate (a,b) electrochemical
cells for evaluation. The cells were discharged at 7.58 mA/g at
24.degree. C., the resultant voltage profiles and capacity is shown
in FIG. 2.
[0087] Electrodes were prepared by adding poly(vinylidene
fluoride-cohexafluoropropylene) (Kynar 2801, Elf Atochem), carbon
black (Super P, MMM) and propylene carbonate (Aldrich) to the
active materials in acetone. The slurry was tape cast, dried for 1
hour at 22.degree. C., and rinsed in 99.8% anhydrous ether
(Aldrich) to extract the propylene carbonate plasticizer. The
electrodes, 1 cm2 disks typically containing 63.+-.1% active
material and 13.+-.1% carbon and 23% Kynar 2801, were tested
electrochemically versus Li metal (Johnson Matthey). The Swagelok
(in-house) or coin (NRC or Hohsen) cells were assembled in a
Helium-filled dry box using Whatman GF/D glass fiber separators
saturated with electrolytes. Electrolyte "a" was 1M LiPF.sub.6 in
ethylene carbonate: dimethyl carbonate (EC:DMC 1:1 in vol.)
electrolyte (Merck), electrolyte "b" was another industry utilized
electrolyte, electrolyte "c" was yet another electrolyte utilized
in industry consisting of lithium bis(trifluoromethane sulfone)
imide (LiN(SO.sub.2CF.sub.3).sub.2, LiTFSI) salt dissolved in a
blend of carbonate solvents. All electrolytes had water contents
less than 25 ppm. The cells were controlled by Mac-Pile (Biologic)
or Maccor battery cycling systems. Cells were cycled under a
constant current of 7.58 mA/g of composite at 24.degree. C., unless
noted otherwise. All specific capacities are calculated utilizing
the weight of all the composite components.
[0088] The materials were evaluated for their electrochemical
properties in lithium metal "half` cells which are utilized in the
art for characterization of electrode materials intended for use in
lithium or lithium ion batteries.
[0089] As can be seen in FIG. 2, the nanocomposites routinely have
specific capacities in excess 400 mAh/g based on the weight of the
entire composite. Accounting for the weight of the matrix in the
CuF.sub.2 nanocomposite, it is clear that exceptional specific
energy densities at greater than 90% of the theoretical composite
capacity are achieved.
[0090] The above fabricated and annealed materials structures were
identified by ex situ x-ray diffraction (XRD) using in some cases
silicon (-325 mesh powder, Johnson Matthey) as internal standard in
a X2 Scintag diffractometer with CuK.alpha. as radiation source. A
least square fit determined a coefficient for a second order
polynomial used to correct all the observed peaks of the spectrum
before lattice parameters calculation. The material microstructure
was analyzed by combined transmission electron microscopy (TEM) and
selected area electron diffraction (SAED). TEM images were obtained
using a Topcon 002B microscope operating at 200 kV. In addition to
imaging, selected area electron diffraction patterns (SAED) from
various areas were obtained to determine the structure of the
phases present.
[0091] All the XRD patterns, as shown in FIG. 3, reveal the
presence of broad diffraction peaks characteristic of primary
CuF.sub.2 crystallite sizes on the order of 10-30 nm. The samples
containing the higher percentages of metaphosphate reveal the
presence of new peaks associated with the formation of
Cu.sub.2FPO.sub.4 second phase. This phase has broad peaks
associated with nano-sized crystallites.
Example 2
Preparation of Copper Fluoride and Phosphate Nanocomposites with
MoO.sub.3 Conductive Matrix with Lithium Metaphosphate Annealed at
High Temperatures
[0092] CM compositions were fabricated as noted in Example 1. After
fabrication, 10 weight % of lithium metaphosphate
(LiPO.sub.3--LiH.sub.2PO.sub.4) was mixed with the CM composition.
A nanocomposite was formed by high energy milling the composition
for a period of 1 h, after which the composition was annealed at
various times and temperatures under a flowing Argon atmosphere.
Specifically, the nanocomposite was annealed at 200.degree. C.,
250.degree. C., and 300.degree. C. The nanocomposites were annealed
for 30 minutes and 2 hours at each temperature. The compositions
were fabricated into electrodes and assembled into duplicate (a,b)
electrochemical cells for evaluation in a manner which has been
described previously. The cells were discharged at 7.58 mA/g at
24.degree. C. and the resultant voltage profiles and capacity is
shown in FIG. 4. As can be seen in FIG. 4, the specific capacity is
exemplary for all the temperatures study with anneal temperatures
at or greater than 200.degree. C., specifically 200.degree. C.,
250.degree. C., and 300.degree. C. These samples revealed high
specific capacities of approximately 400 mAh/g based on the weight
of the entire composite.
[0093] FIG. 5 shows the XRD patterns of the fabricated samples
including a CM composition with no phosphate additions. All the XRD
patterns reveal the presence of broad diffraction peaks
characteristic of primary CuF.sub.2 crystallite sizes on the order
of 10-30 nm. The samples which were annealed at temperatures
greater than 200.degree. C. reveal the presence of new peaks
associated with the formation of Cu.sub.2FPO.sub.4 second phase of
nanosized domains.
Example 3
Preparation of Copper Fluoride and Phosphate Nanocomposites with
MoO.sub.3 Conductive Matrix with Lithium Dihydrogen Phosphate
[0094] CM compositions were fabricated as described in Example 1.
After fabrication, various weight percentages of lithium dihydrogen
phosphate (LiH.sub.2PO.sub.4) were mixed with the CM composition.
Specifically, 10% lithium dihydrogen phosphate, 15% lithium
dihydrogen phosphate, 20% lithium dihydrogen phosphate and 30%
lithium dihydrogen phosphate were mixed with the CM. A
nanocomposite was formed by high energy milling the composition for
a period of 1 h after which, the composition was annealed at
250.degree. C. for a period of 30 minutes in Argon. The
compositions were fabricated into electrodes and assembled in
duplicate (a, b) into electrochemical cells for evaluation as
described above. The cells were discharged at 7.58 mA/g at
24.degree. C. and the resultant voltage profiles and capacity is
shown in FIG. 6. The specific capacity is exemplary for all the
compositions with many compositions achieving greater than 400
mAh/g based on the weight of the entire composite.
[0095] FIG. 7 shows XRD patterns of the samples. All the XRD
patterns reveal the presence of broad diffraction peaks
characteristic of primary CuF.sub.2 crystallite sizes on the order
of 10-30 nm. The samples containing the higher percentages of
LiH.sub.2PO.sub.4 reveal the presence of new peaks associated with
the formation of greater quantities of a nanocrystalline
Cu.sub.2FPO.sub.4 second phase.
Example 4
Copper Fluoride and Phosphate Nanocomposites with MoO.sub.3
Conductive Matrix with Hydrogen Phosphate
[0096] CM compositions were fabricated as described above in
Example 1. After fabrication, various weight percentages of
hydrogen phosphate H.sub.3PO.sub.4 were mixed with the CM
composition. Specifically, 10 weight % of hydrogen phosphate, 15
weight % of hydrogen phosphate, 20 weight % of hydrogen phosphate,
and 30 weight percent % of hydrogen phosphate were mixed with CM. A
nanocomposite was formed by high energy milling the composition for
a period of 1 h after which the composition was annealed at
250.degree. C. for a period of 30 minutes in Argon. The
compositions were fabricated into electrodes and assembled in
duplicate (a, b) into electrochemical cells for evaluation in a
manner described above. The cells were discharged at 7.58 mA/g at
24.degree. C. and the resultant voltage profiles and capacity is
shown in FIG. 8. As can be seen in FIG. 8, the specific capacity is
high for all the compositions with many compositions achieving
greater than 325 mAh/g based on the weight of the entire
composite.
[0097] FIG. 9 shows the x-ray diffraction patterns of the samples.
All the XRD patterns reveal the presence of broad diffraction peaks
characteristic of primary CuF.sub.2 crystallite sizes on the order
of 10-30 nm. The samples containing the higher percentages of
H.sub.3PO.sub.4 do not reveal the presence of the new peaks
associated with the formation of Cu.sub.2FPO.sub.4 second phase.
Therefore the phosphate phase is x-ray amorphous.
Example 5
Evaluation of Performance of Copper Fluoride and Phosphate
Nanocomposites
[0098] The copper fluoride compositions described in Examples 1-4
were fabricated into electrodes and placed into electrochemical
cells to evaluate their performance as positive electrode materials
in lithium batteries. To evaluate charge retention under the most
severe conditions, the cells were discharged to a capacity of 100
mAh/g at 24.degree. C. (partial discharge). After this period the
cells were placed into storage at 60.degree. C. for a period of one
week. After the storage period the cells were placed back at
24.degree. C. and the discharge was continued. The total specific
capacity was calculated and tabulated in TABLE 1 below. It is
readily apparent that the use of phosphate as described in the
various examples resulted in exceptional improvement of the
elevated temperature storage capability. As can be seen the
CuF.sub.2:MoO.sub.3 nanocomposite without any phosphate had an
accumulated capacity of 100 mAh/g, of which 100 mAh/g was the
capacity recorded at room temperature before 60.degree. C. storage.
Therefore, no capacity was left in the cell after storage at
elevated temperature. In sharp contrast, the samples which
contained phosphate exhibit an extraordinary capability to retain
specific capacity at elevated temperatures. Indeed, the specific
capacity was found to be on the order of the discharge specific
capacity obtained at room temperature as defined by the above
examples. Of the various phosphates shown here, LiH.sub.2PO.sub.4
exhibited the best capacity retention. It should also be noted that
although a variety of electrolytes were utilized in the evaluation,
only small differences were seen to exist in their effect on the
storage characteristics of the nanocomposite.
TABLE-US-00001 TABLE 1 Phosphate Anneal Electro- Sam- PDD
Composition wt % T (.degree. C.) t(h) lyte ple 60.degree. C. No
phosphate 0% A a 100 mAh/g No phosphate 0% A b 100 mAh/g No
phosphate 0% B a 100 mAh/g No phosphate 0% B b 100 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h A a 276 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h A b 289 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h B a 311 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h B b 337 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h C a 308 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h A a 269 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h A b 274 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h B a 235 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 10% 250.degree. C. 2 h B b 278 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h A a 243 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h A b 248 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h B a 311 mAh/g
LiPO.sub.3LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h B b 98 mAh/g
H.sub.3PO.sub.4 15% 250.degree. C. 0.5 h B a 301 mAh/g
H.sub.3PO.sub.4 15% 250.degree. C. 0.5 h B b 304 mAh/g
H.sub.3PO.sub.4 20% 250.degree. C. 0.5 h B a 303 mAh/g
LiH.sub.2PO.sub.4 10% 250.degree. C. 0.5 h A a 362 mAh/g
LiH.sub.2PO.sub.4 10% 250.degree. C. 0.5 h A b 350 mAh/g
LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h B a 365 mAh/g
LiH.sub.2PO.sub.4 15% 250.degree. C. 0.5 h B b 359 mAh/g
LiH.sub.2PO.sub.4 20% 250.degree. C. 0.5 h B a 356 mAh/g
LiH.sub.2PO.sub.4 20% 250.degree. C. 0.5 h B b 359 mAh/g
Example 6
Bismuth Fluoride and Phosphate Nanocomposite with MoS.sub.2
Conductive Matrix with Lithium Metaphosphate
[0099] BiF3 and a conductive matrix of 20% MoS.sub.2 were sealed
under Helium and a nanocomposite was fabricated through the high
energy milling of the respective components for various times in a
Spex 8000 milling apparatus. The nanocomposite was annealed under
Argon. To this composition 5 weight % of lithium metaphosphate was
high energy milled and the composite was heat treated at
200.degree. C. under argon atmosphere. The resulting plot of
capacity vs. cycle life is shown in FIG. 10 and shows a marked
improvement in the capacity retention as a function of cycle life
for a variety of compositions containing phosphate vs. the
non-phosphate containing compositions.
Example 7
[0100] In order to show good electrochemical performance in a
nanocomposite using a drastically different electronically
conductive matrix besides molybdenum and oxygen, a nanocomposite
was fabricated utilizing an alloy composition consisting of bismuth
and telluride. A nanocomposite was formed by high energy milling
CuF.sub.2 with a 10 weight % LiH.sub.2PO.sub.4 composition for a
period of 1 h, after which the composition was annealed at
250.degree. C. for a period of 30 minutes in Argon. A 10 weight %
conductive matrix of bismuth telluride (Bi.sub.2Te.sub.3) was
milled within the nanocomposite for 45 minutes. The compositions
were fabricated into electrodes and assembled into electrochemical
cells for evaluation in a manner which has been described
previously. The cells were discharged at 7.58 mA/g at 24.degree. C.
and the resultant voltage profiles and capacity is shown in the
figure below.
[0101] As can be seen in FIG. 11, even utilizing the alternative
electronically conducting matrices besides the molybdates described
above, that improved performance can be obtained with copper
fluoride nanocomposites containing phosphate.
[0102] While the present invention has been described with respect
to what is presently considered to be the preferred embodiment(s),
it is to be understood that the invention is not limited to the
disclosed embodiment(s). To the contrary, the invention is intended
to cover various modifications and equivalent compositions and/or
arrangements included within the spirit and scope of the appended
claims. The scope of the following claims is to be accorded the
broadest interpretation so as to encompass all such modifications
and equivalent structures and functions.
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