U.S. patent application number 15/693926 was filed with the patent office on 2018-08-09 for rechargeable aluminum ion battery.
The applicant listed for this patent is EVERON24 LLC. Invention is credited to Nikhil A. KORATKAR, Rahul MUKHERJEE.
Application Number | 20180226831 15/693926 |
Document ID | / |
Family ID | 58488696 |
Filed Date | 2018-08-09 |
United States Patent
Application |
20180226831 |
Kind Code |
A9 |
MUKHERJEE; Rahul ; et
al. |
August 9, 2018 |
Rechargeable Aluminum Ion Battery
Abstract
A rechargeable battery using a solution of an aluminum salt as
an electrolyte is disclosed, as well as methods of making the
battery and methods of using the battery.
Inventors: |
MUKHERJEE; Rahul; (Troy,
NY) ; KORATKAR; Nikhil A.; (Halfmoon, NY) |
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Applicant: |
Name |
City |
State |
Country |
Type |
EVERON24 LLC |
Burlington |
MA |
US |
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Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20180102671 A1 |
April 12, 2018 |
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|
Family ID: |
58488696 |
Appl. No.: |
15/693926 |
Filed: |
September 1, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15290599 |
Oct 11, 2016 |
9819220 |
|
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15693926 |
|
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62238935 |
Oct 8, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/58 20130101; H02J
7/35 20130101; H01M 4/505 20130101; H01M 2300/0002 20130101; H02J
3/386 20130101; H01M 4/525 20130101; Y02E 60/10 20130101; H01M
10/36 20130101; H01M 4/38 20130101; H01M 10/4235 20130101; H01M
4/485 20130101; Y02E 10/56 20130101; Y02E 10/76 20130101; Y02B
10/30 20130101; H01M 4/587 20130101; H01M 4/463 20130101; H01M
10/44 20130101; H02J 3/383 20130101 |
International
Class: |
H02J 7/35 20060101
H02J007/35; H01M 4/58 20060101 H01M004/58; H01M 4/525 20060101
H01M004/525; H01M 4/485 20060101 H01M004/485; H01M 4/46 20060101
H01M004/46; H01M 10/36 20060101 H01M010/36; H02J 3/38 20060101
H02J003/38; H01M 4/38 20060101 H01M004/38; H01M 10/44 20060101
H01M010/44; H01M 4/505 20060101 H01M004/505; H01M 4/587 20060101
H01M004/587; H01M 10/42 20060101 H01M010/42 |
Claims
1. A battery comprising: an anode comprising aluminum, an aluminum
alloy or an aluminum compound; a cathode; a porous separator
comprising an electrically insulating material that prevents direct
contact of the anode and the cathode; and an electrolyte comprising
an aqueous solution of an aluminum salt, wherein the electrolyte is
in electrical contact with the anode and the cathode, and wherein
current is carried between the anode and cathode by ions comprising
aluminum during charge and discharge of the battery.
2. The battery of claim 1 wherein the aluminum alloy comprises
aluminum and at least one element selected from the group
consisting of manganese, magnesium, lithium, zirconia, iron,
cobalt, tungsten, vanadium, nickel, copper, silicon, chromium,
titanium, tin and zinc.
3. The battery of claim 1 wherein the anode comprises a treatment
that increases the hydrophilic properties of the anode surface that
is in contact with the electrolyte.
4. The battery of claim 3 wherein the treatment comprises an alkali
metal hydroxide selected from the group consisting of lithium
hydroxide, sodium hydroxide, potassium hydroxide and mixtures
thereof.
5. The battery of claim 1 wherein the anode comprises an aluminum
compound selected from the group consisting of an aluminum
transition metal oxide (Al.sub.xM.sub.yO.sub.z, where M is a
transition metal selected from the group consisting of iron,
vanadium, titanium, molybdenum, copper, nickel, zinc, tungsten,
manganese, chromium, cobalt and mixtures thereof and x, y, and z
range from 0 to 8, inclusive); an aluminum transition metal sulfide
(Al.sub.xM.sub.yS.sub.z, where M is a transition metal selected
from the group consisting of iron, vanadium, titanium, molybdenum,
copper, nickel, zinc, tungsten, manganese, chromium, cobalt and
mixtures thereof and x, y, and z range from 0 to 8, inclusive);
aluminum lithium cobalt oxide (AlLi.sub.3CoO.sub.2); lithium
aluminum hydride (LiAlH.sub.4); sodium aluminum hydride
(NaAlH.sub.4); potassium aluminum fluoride (KAlF.sub.4); and
mixtures thereof.
6. The battery of claim 1 wherein the aluminum salt is selected
from the group consisting of aluminum nitrate, aluminum sulfate,
aluminum phosphate, aluminum bromide hexahydrate, aluminum
fluoride, aluminum fluoride trihydrate, aluminum iodide
hexahydrate, aluminum perchlorate, aluminum hydroxide, and
combinations thereof.
7. The battery of claim 1 wherein the electrolyte is an aqueous
solution of the aluminum salt.
8. The battery of claim 1 wherein the electrolyte is an aqueous
solution of aluminum nitrate.
9. The battery of claim 8 wherein the electrolyte is an 0.05-5 M
aqueous solution of aluminum nitrate.
10. The battery of claim 1 wherein the electrolyte comprises a
solvent selected from the group consisting of water, ethanol,
N-methyl pyrrolidone, dimethyl sulfoxide and mixtures thereof.
11. The battery of claim 1 wherein the cathode comprises a material
selected from the group consisting of lithium manganese oxide,
acid-treated lithium manganese oxide, lithium metal manganese oxide
(where the metal is selected from the group consisting of nickel,
cobalt, aluminum, chromium and combinations thereof), acid-treated
lithium metal manganese oxide, graphite metal composite (where the
metal is an electrically conductive metal selected from the group
consisting of nickel, iron, copper, cobalt, chromium, aluminum and
mixtures thereof), graphite-graphite oxide, manganese dioxide and
graphene.
12. The battery of claim 11 wherein the cathode is an acid treated
cathode comprising lithium.
13. The battery of claim 1 wherein the porous separator comprises a
material selected from the group consisting of polyethylene,
polytetrafluoroethylene, polyvinyl chloride, ceramic, polyester,
rubber, polyolefins, glass mat, polypropylene, a mixed cellulose
ester, nylon, glass microfiber and mixtures and combinations
thereof.
14. The battery of claim 1 wherein the anode comprises aluminum
metal, the cathode comprises graphite-graphite oxide, and the
electrolyte is an aqueous solution comprising aluminum nitrate.
15. The battery of claim 1 wherein the anode comprises aluminum
metal, the cathode comprises acid-treated lithium manganese oxide,
and the electrolyte is an aqueous solution comprising aluminum
nitrate.
16. The battery of claim 1 wherein the anode comprises aluminum
metal, the cathode comprises lithium manganese oxide, the aluminum
salt comprises aluminum nitrate and the porous separator comprises
a material selected from the group consisting of polyethylene,
polytetrafluoroethylene, polyvinyl chloride, ceramic, polyester,
rubber, polyolefins, glass mat, polypropylene, a mixed cellulose
ester, nylon, glass microfiber and mixtures and combinations
thereof.
17. The battery of claim 1 wherein the average pore size of the
porous separator is about 0.067 .mu.m to about 1.2 .mu.m.
18. The battery of claim 1 wherein the anode, cathode, and
electrolyte are configured so that current carried by ions
comprising aluminum flows from the anode to the electrolyte during
discharge of the battery.
19. The battery of claim 1 wherein the anode, cathode, and
electrolyte are configured so that current carried by ions
comprising aluminum flows from the electrolyte to the cathode
during discharge of the battery.
20. The battery of claim 1 wherein the ions comprising aluminum are
selected from the group consisting of the hydroxyaluminate anion,
Al(OH).sub.4.sup.1-, the tetrachloroaluminate ion,
AlCl.sub.4.sup.1-, the tetrahydroaluminate ion, AlH.sub.4.sup.1-,
and the hexafluoroaluminate ion, AlF.sub.6.sup.1-
21. The battery of claim 1 wherein the ions comprising aluminum are
Al(OH).sub.4.sup.1- ions.
22. A battery comprising: an anode comprising a material selected
from the group consisting of aluminum metal; an aluminum alloy
comprising aluminum and at least one element selected from the
group consisting of manganese, magnesium, lithium, zirconia, iron,
cobalt, tungsten, vanadium, nickel, copper, silicon, chromium,
titanium, tin and zinc; an aluminum compound selected from the
group consisting of an aluminum transition metal oxide
(Al.sub.xM.sub.yO.sub.z, where M is a transition metal selected
from the group consisting of iron, vanadium, titanium, molybdenum,
copper, nickel, zinc, tungsten, manganese, chromium, cobalt and
mixtures thereof and x, y, and z range from 0 to 8, inclusive); an
aluminum transition metal sulfide, (Al.sub.xM.sub.yS.sub.z, where M
is a transition metal selected from the group consisting of iron,
vanadium, titanium, molybdenum, copper, nickel, zinc, tungsten,
manganese, chromium, cobalt and mixtures thereof and x, y, and z
range from 0 to 8, inclusive); aluminum lithium cobalt oxide
(AlLi.sub.3CoO.sub.2); lithium aluminum hydride (LiAlH.sub.4);
sodium aluminum hydride (NaAlH.sub.4); potassium aluminum fluoride
(KAlF.sub.4); or mixtures thereof; a cathode comprising a material
selected from the group consisting of lithium manganese oxide,
acid-treated lithium manganese oxide, lithium metal manganese oxide
(where the metal is selected from the group consisting of nickel,
cobalt, aluminum, chromium and combinations thereof), acid-treated
lithium metal manganese oxide, graphite metal composite (where the
metal is an electrically conductive metal selected from the group
consisting of nickel, iron, copper, cobalt, chromium, aluminum and
mixtures thereof), graphite-graphite oxide, manganese dioxide and
graphene; and an electrolyte comprising an aqueous solution of an
aluminum salt selected from the group consisting of aluminum
nitrate, aluminum sulfate, aluminum phosphate, aluminum bromide
hexahydrate, aluminum fluoride, aluminum fluoride trihydrate,
aluminum iodide hexahydrate, aluminum perchlorate, aluminum
hydroxide, and combinations thereof, wherein the electrolyte is in
electrical contact with the anode and the cathode, and wherein
current is carried between anode and cathode by ions comprising
aluminum during change and discharge of the battery.
23. The battery of claim 22 further comprising a porous separator
comprising an electrically insulating material that prevents direct
contact of the anode and the cathode, wherein the porous separator
comprises a material selected from the group consisting of
polyethylene, polytetrafluoroethylene, polyvinyl chloride, ceramic,
polyester, rubber, polyolefins, glass mat, polypropylene, a mixed
cellulose ester, nylon, glass microfiber and mixtures and
combinations thereof.
24. The battery of claim 22 wherein the anode comprises aluminum
metal, the cathode comprises graphite-graphite oxide, and the
electrolyte is an aqueous solution comprising aluminum nitrate.
25. The battery of claim 22 wherein the anode comprises aluminum
metal, the cathode comprises acid-treated lithium manganese oxide,
and the electrolyte is an aqueous solution comprising aluminum
nitrate.
26. The battery of claim 22 wherein the anode, cathode, and
electrolyte are configured so that current carried by ions
comprising aluminum flows from the anode to the electrolyte during
discharge of the battery.
27. The battery of claim 22 wherein the anode, cathode, and
electrolyte are configured so that current carried by ions
comprising aluminum flows from the electrolyte to the cathode
during discharge of the battery.
28. The battery of claim 22 wherein the ions comprising aluminum
are selected from the group consisting of the hydroxyaluminate
anion, Al(OH).sub.4.sup.1-, the tetrachloroaluminate ion,
AlCl.sub.4.sup.1-, the tetrahydroaluminate ion, AlH.sub.4.sup.1-,
and the hexafluoroaluminate ion, AlF.sub.6.sup.1-
29. The battery of claim 22 wherein the ions comprising aluminum
are Al(OH).sub.4.sup.1- ions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/290,599, filed Oct. 11, 2016, which claims
benefit under 35 U.S.C. .sctn. 119 of U.S. Provisional Application
Ser. No. 62/238,935, filed Oct. 8, 2015, the contents of both of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present disclosure relates to rechargeable batteries
using charge carriers comprising aluminum ions, and particularly
batteries with reduced toxic components to minimize human health
hazards and environmental damage.
Description of the Background
[0003] With an increase in interest in generating electricity from
renewable energy sources such as wind and solar, it has become
increasingly important to identify a viable battery storage system.
Lead acid batteries, for instance, are the most widely used battery
technology for grid storage owing to their low cost (about
$100-$150/kWh). However, lead acid batteries have a comparatively
low gravimetric energy density (30-50 Wh/kg) and a poor cycle life,
between 500 and 1000 charge/discharge cycles, based on the low
depths of discharge (50-75%). In addition, lead acid batteries have
significant safety problems associated with handling and disposal,
due to the presence of sulfuric acid and toxic lead components.
Reports of increased lead poisoning and acid-related injuries among
workers and children exposed to unsafe handling and disposal of
lead acid batteries, have raised strong concerns over large-scale
implementation of lead acid batteries as storage for electricity
generated from renewable energy sources.
[0004] The search for economical alternatives for electrical
storage that lack the environmental and health risks of lead acid
batteries has not been successful. One alternative, sodium ion
batteries, are estimated to reach a price of about $250/kWh by
2020, but the volumetric energy density of sodium ion battery
technology is lower than that of lead acid batteries at less than
about 30 Wh/L.
[0005] Another alternative, vanadium redox flow batteries, offer
high capacity, long discharge times and high cycle life, but have
relatively low gravimetric and volumetric energy densities, and are
expensive due to the high cost of vanadium and other components.
Liquid metal batteries on the other hand are based on ion exchange
between two immiscible molten salt electrolytes, but must operate
at high temperatures, up to 450.degree. C., rely on a complicated
lead-antimony-lithium composite for ion exchange, and such systems
have problems of flammability and toxicity.
SUMMARY OF THE INVENTION
[0006] A rechargeable battery using an electrolyte comprising
aluminum ions is disclosed, as well as methods of making the
battery and methods of using the battery.
[0007] In certain embodiments, a battery is disclosed that includes
an anode comprising aluminum, an aluminum alloy or an aluminum
compound, a cathode, a porous separator comprising an electrically
insulating material that prevents direct contact of the anode and
the cathode, and an electrolyte comprising a solution of an
aluminum salt, wherein the electrolyte is in electrical contact
with the anode and the cathode. In preferred embodiments, the
battery is a rechargeable battery, that is, a secondary
battery.
[0008] In certain embodiments, the anode is an aluminum alloy
comprising aluminum and at least one element selected from the
group consisting of manganese, magnesium, lithium, zirconia, iron,
cobalt, tungsten, vanadium, nickel, copper, silicon, chromium,
titanium, tin and zinc. In certain embodiments, the anode is
aluminum that has received a treatment that is effective to
increase the hydrophilic properties of the anode surface that is in
contact with the electrolyte. In certain embodiments, the surface
treatment comprises the step of contacting a surface of the
aluminum with an aqueous solution of an alkali metal hydroxide.
Typically, the alkali metal hydroxide selected from the group
consisting of lithium hydroxide, sodium hydroxide, potassium
hydroxide and mixtures thereof. In certain embodiments, anode is an
aluminum metal foil or an aluminum alloy foil.
[0009] In certain embodiments, the anode is an aluminum compound
selected from the group consisting of an aluminum transition metal
oxide (Al.sub.xM.sub.yO.sub.z, where M is a transition metal
selected from the group consisting of iron, vanadium, titanium,
molybdenum, copper, nickel, zinc, tungsten, manganese, chromium,
cobalt and mixtures thereof and x, y, and z range from 0 to 8,
inclusive); an aluminum transition metal sulfide,
(Al.sub.xM.sub.yS.sub.z, where M is a transition metal selected
from the group consisting of iron, vanadium, titanium, molybdenum,
copper, nickel, zinc, tungsten, manganese, chromium, cobalt and
mixtures thereof and x, y, and z range from 0 to 8, inclusive);
aluminum lithium cobalt oxide (AlLi.sub.3CoO.sub.2); lithium
aluminum hydride (LiAlH.sub.4); sodium aluminum hydride
(NaAlH.sub.4); potassium aluminum fluoride (KAlF.sub.4); and
mixtures thereof.
[0010] In certain embodiments, the electrolyte is an aqueous
solution of an aluminum salt selected from the group consisting of
aluminum nitrate, aluminum sulfate, aluminum phosphate, aluminum
bromide hexahydrate, aluminum fluoride, aluminum fluoride
trihydrate, aluminum iodide hexahydrate, aluminum perchlorate,
aluminum hydroxide, and combinations thereof. In certain
embodiments, the molarity of the aluminum salt ranges from 0.05 M
to 5 M and the concentration of water ranges from 5 weight % to 95
weight %.
[0011] In certain embodiments, the electrolyte further comprises an
alkali metal hydroxide selected from the group consisting of
lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium
hydroxide, calcium hydroxide, magnesium hydroxide and mixtures
thereof. In certain embodiments, the electrolyte comprises an
aqueous solution of aluminum nitrate and lithium hydroxide in a
molar ratio of about 1:1 to about 1:10. In certain embodiments, the
electrolyte comprises a polymer selected from the group consisting
of polytetrafluoroethylene, acetonitrile butadiene styrene, styrene
butadiene rubber, ethyl vinyl acetate, poly(vinylidene
fluoride-co-hexafluoropropylene), polymethyl methacrylate, and
mixtures thereof.
[0012] In certain embodiments, the electrolyte comprises an
aluminum halide selected from the group consisting of aluminum
chloride, aluminum bromide, aluminum iodide, and mixtures thereof
and a 1-ethyl methylimidazolium halide selected from the group
consisting of 1-ethyl methylimidazolium chloride, 1-ethyl
methylimidazolium bromide, 1-ethyl methylimidazolium iodide and
mixtures thereof. In certain embodiments, the aluminum halide and
the 1-ethyl methylimidazolium halide are present in the ratio of
1:1 to 5:1 (weight:weight).
[0013] In certain embodiments, the electrolyte comprises a solvent
selected from the group consisting of water, ethanol, N-methyl
pyrrolidone, dimethyl sulfoxide and mixtures thereof.
[0014] In certain embodiments, the cathode comprises a material
selected from the group consisting of lithium manganese oxide,
acid-treated lithium manganese oxide, lithium metal manganese oxide
(where the metal is selected from the group consisting of nickel,
cobalt, aluminum, chromium and combinations thereof), acid-treated
lithium metal manganese oxide, graphite metal composite (where the
metal is an electrically conductive metal selected from the group
consisting of nickel, iron, copper, cobalt, chromium, aluminum and
mixtures thereof), graphite-graphite oxide, manganese dioxide and
graphene. In certain preferred embodiments, cathodes comprising
lithium have been subjected to acid treatment. In certain preferred
embodiments, the anode comprises aluminum metal, the cathode
comprises graphite-graphite oxide, and the aluminum salt comprises
aluminum nitrate. In other preferred embodiments, the anode
comprises aluminum metal, the cathode comprises acid-treated
lithium manganese oxide, and the aluminum salt comprises aluminum
nitrate.
[0015] In certain embodiments, the porous separator comprises a
material selected from the group consisting of polyethylene,
polytetrafluoroethylene, polyvinyl chloride, ceramic, polyester,
rubber, polyolefins, glass mat, polypropylene, a mixed cellulose
ester, nylon, glass microfiber and mixtures and combinations
thereof. The separators may be treated with or mixed with
hydrophilic functional groups, monomers or polymers, including but
not limited to acrylic acid, diethyleneglycol-dimethacrylate,
cellulose acetate and silicon oxide, in order to introduce
hydrophilicity for use with aqueous electrolytes. In certain
embodiments, the porous separator has an average pore size of about
0.067 .mu.m to about 1.2 .mu.m.
[0016] In certain embodiments, a battery is disclosed that
comprises an anode comprising aluminum, an aluminum alloy
comprising aluminum and at least one element selected from the
group consisting of manganese, magnesium, lithium, zirconia, iron,
cobalt, tungsten, vanadium, nickel, copper, silicon, chromium,
titanium, tin and zinc; an aluminum compound selected from the
group consisting of an aluminum transition metal oxide
(Al.sub.xM.sub.yO.sub.z, where M is a transition metal selected
from the group consisting of iron, vanadium, titanium, molybdenum,
copper, nickel, zinc, tungsten, manganese, chromium, cobalt and
mixtures thereof and x, y, and z range from 0 to 8, inclusive); an
aluminum transition metal sulfide, (Al.sub.xM.sub.yS.sub.z, where M
is a transition metal selected from the group consisting of iron,
vanadium, titanium, molybdenum, copper, nickel, zinc, tungsten,
manganese, chromium, cobalt and mixtures thereof and x, y, and z
range from 0 to 8, inclusive); aluminum lithium cobalt oxide
(AlLi.sub.3CoO.sub.2); lithium aluminum hydride (LiAlH.sub.4);
sodium aluminum hydride (NaAlH.sub.4); potassium aluminum fluoride
(KAlF.sub.4); or mixtures thereof; a cathode comprising a material
selected from the group consisting of lithium manganese oxide,
acid-treated lithium manganese oxide, lithium metal manganese oxide
(where the metal is selected from the group consisting of nickel,
cobalt, aluminum, chromium and combinations thereof), acid-treated
lithium metal manganese oxide, graphite metal composite (where the
metal is an electrically conductive metal selected from the group
consisting of nickel, iron, copper, cobalt, chromium, aluminum and
mixtures thereof), graphite-graphite oxide, manganese dioxide and
graphene; and an electrolyte comprising an aqueous solution of an
aluminum salt selected from the group consisting of aluminum
nitrate, aluminum sulfate, aluminum phosphate, aluminum bromide
hexahydrate, aluminum fluoride, aluminum fluoride trihydrate,
aluminum iodide hexahydrate, aluminum perchlorate, aluminum
hydroxide, and combinations thereof. In certain embodiments, the
molarity of the aluminum salt ranges from 0.05 M to 5 M and the
concentration of water ranges from 5 weight % to 95 weight %.
Typically, the battery further comprises a porous separator
comprising an electrically insulating material that prevents direct
contact of the anode and the cathode. In certain embodiments, the
porous separator comprises a material selected from the group
consisting of polyethylene, polytetrafluoroethylene, polyvinyl
chloride, ceramic, polyester, rubber, polyolefins, glass mat,
polypropylene, a mixed cellulose ester, nylon, glass microfiber and
mixtures and combinations thereof. The separators maybe treated
with or mixed with hydrophilic functional groups, monomers or
polymers, including but not limited to acrylic acid,
diethyleneglycol-dimethacrylate, cellulose acetate and silicon
oxide, in order to introduce hydrophilicity for use with aqueous
electrolytes. In certain embodiments, the porous separator has an
average pore size of about 0.067 .mu.m to about 1.2 .mu.m.
[0017] Also disclosed are methods of using a rechargeable battery
that includes an anode comprising aluminum, an aluminum alloy or an
aluminum compound, a cathode, a porous separator comprising an
electrically insulating material that prevents direct contact of
the anode and the cathode and an electrolyte comprising an aqueous
solution of an aluminum salt. In certain embodiments, a system is
disclosed that includes at least one such rechargeable battery that
is operatively connected to a controller, wherein the controller is
adapted to be operatively connected to a source of electrical power
and to a load. In certain embodiments, the controller is effective
to control the charging of the battery by the source of electrical
power. In certain embodiments, the controller is effective to
control the discharging of the battery by the load. In certain
embodiments, the controller is adapted to provide a discharge
pattern that is a combination of high and low current density
galvanostatic steps. In certain embodiments, the source of
electrical power is a solar panel or wind-powered generator. In
certain embodiments, the load is a local electrical load or a power
distribution grid.
[0018] The above described and other features are exemplified by
the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The foregoing and other features and advantages will be
apparent from the following more particular description of
exemplary embodiments of the disclosure, as illustrated in the
accompanying drawings, in which like reference characters refer to
the same parts throughout the different views. The drawings are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the disclosure.
[0020] FIG. 1A is a photograph of aluminum foil suitable for use as
an anode that has been treated with a drop of an aqueous solution
of lithium hydroxide; FIG. 1B is a photograph of the piece of the
treated aluminum foil of FIG. 1A showing a change in the appearance
of the drop of the aqueous solution of lithium hydroxide; FIG. 1C
is a photograph of the piece of treated aluminum foil of FIG. 1B
showing the greyish-white appearance of the aluminum foil following
the drying of the lithium hydroxide solution; FIG. 1D is a
photograph of the piece of treated aluminum foil of FIG. 1C showing
the effect of placing a drop of deionized water on the treated
aluminum foil indicating an increase in hydrophilicity of the
treated aluminum foil; and FIG. 1E is a photograph of a drop of
deionized water on untreated aluminum foil for comparison to FIG.
1D.
[0021] FIG. 2 is a schematic diagram of an exploded view of a test
battery 100 in a coin cell format, showing the positive case 110, a
spring 120, a first spacer 130, the cathode 140, the separator 150,
the anode 160, a second spacer 170 and the negative case 180.
[0022] FIG. 3 is an x-ray photoelectron spectroscopy (XPS) profile
of carbon sheets following a 100% depth of discharge, showing a
strong peak corresponding to Al 2p transition, associated with the
presence of gibbsite, Al(OH).sub.3, crystals.
[0023] FIG. 4A shows the voltage profile that was produced by
applying current at a current density of 0.1 mA/cm.sup.2 to a test
battery having an anode comprising an aluminum foil treated with
LiOH as described in Example 1, a cathode comprising acid-treated
lithium manganese oxide, a 25 .mu.m thick polypropylene separator
with an average pore size of 0.067 and a 0.5 M aqueous aluminum
nitrate electrolyte. FIG. 4B shows the voltage profile that was
produced by applying current at a current density of 0.1
mA/cm.sup.2 to a test battery having an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising graphite-graphite oxide, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 and a
0.5 M aqueous aluminum nitrate electrolyte. The observed average
operating voltage is significantly higher with the use of
acid-treated lithium manganese oxide cathodes, possibly owing to
the higher activation energy for diffusion and intercalation of
ions. Carbon is known to possess a sufficiently low activation
energy for diffusion and intercalation of metal ions (the
intercalation voltage of lithium ions in carbon against a lithium
metal occurs at about 100 mV).
[0024] FIG. 5A shows the battery capacity as a function of cycle
index of a battery having an anode comprising an aluminum foil
treated with LiOH as described in Example 1, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 and a
0.5 M aqueous aluminum nitrate electrolyte and a graphite-graphite
oxide composite cathode. The coulombic efficiency was estimated to
be close to 100%, indicating efficient and reversible charge and
discharge kinetics. FIG. 5B shows the battery capacity as a
function of cycle index of a battery having an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a 25
.mu.m thick polypropylene separator with an average pore size of
0.067 and a 0.5 M aqueous aluminum nitrate electrolyte and an
acid-treated Li.sub.1-xMnO.sub.2 cathode. The reduction in capacity
after over 800 charge/discharge cycles is only about 3% of the
original capacity.
[0025] FIG. 6A shows sequential cyclic voltammetry profiles of a
battery having an anode comprising an aluminum foil treated with
LiOH as described in Example 1, a 25 .mu.m thick polypropylene
separator with an average pore size of 0.067 and a 0.5 M aqueous
aluminum nitrate electrolyte and an acid-treated lithium manganese
oxide cathode. FIG. 6B shows sequential cyclic voltammetry profiles
of a battery having an anode comprising an aluminum foil treated
with LiOH as described in Example 1, a 25 .mu.m thick polypropylene
separator with an average pore size of 0.067 .mu.m and a 0.5 M
aqueous aluminum nitrate electrolyte and a graphite-graphite oxide
cathode. The test batteries in the coin cell format were cycled at
various voltage sweep rates between 10 mV/sec and 50 mV/sec within
a voltage range of 0 V and 1.5 V.
[0026] FIG. 7A shows the results of electrochemical impedance
spectroscopy (EIS) of a test cell having an aluminum anode and an
acid-treated lithium manganese oxide cathode. FIG. 7B shows the
results of electrochemical impedance spectroscopy (EIS) of a test
cell having an aluminum anode and a graphite-graphite oxide
cathode. Insets show the Randles equivalent circuit used to fit the
spectra.
[0027] FIG. 8A is a schematic representation of a prismatic cell
80.
[0028] FIG. 8B illustrates the discharge voltage profile of a
prismatic cell rated at 1 mAh. The cell had an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising acid-treated lithium manganese oxide, a 25 .mu.m
thick polypropylene separator with an average pore size of 0.067
.mu.m, 0.5 M aqueous aluminum nitrate electrolyte and were tested
at 10 .mu.A/cm.sup.2.
[0029] FIG. 9A is a schematic representation of a pouch cell
90.
[0030] FIG. 9B illustrates the discharge profile of a pouch cell
comprising 0.8 cm.times.1 cm electrodes and hydrophilic
polypropylene separators. The cell had an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising acid-treated lithium manganese oxide, a 25 .mu.m
thick polypropylene separator with an average pore size of 0.067
.mu.m, 0.5 M aqueous aluminum nitrate electrolyte and were tested
at about 25 .mu.A/cm.sup.2.
[0031] FIG. 10 is a block diagram of a system 800 that incorporates
the battery 810 of the present disclosure, showing a controller 820
that is operatively connected to battery 810, a source of
electrical power 830, a local electrical load 840 and an electrical
power distribution grid 850.
[0032] FIG. 11 compares the discharge and charging properties of
two batteries differing in electrolyte composition: one battery
having a 0.5 M Al(NO.sub.3).sub.3 (aq) electrolyte (curve 1) and
another battery having a 0.5 M Al(NO.sub.3).sub.3 and 2 M LiOH (aq)
electrolyte (curve 2). Each battery was assembled in a 2032 coin
cell format and had an anode comprising an aluminum foil treated
with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 and was
tested at current densities of 10 .mu.A/cm.sup.2.
[0033] FIG. 12 illustrates the effect of separator pore size on the
average discharge potential produced at a given current density,
where pentagons (1) represent measurements made on a battery having
a polypropylene separator with 0.067 .mu.m pores, a triangle (2)
represents measurements made on a battery having a mixed cellulose
ester separator with 0.20 .mu.m pores, a circle (3) represents
measurements made on a battery having a nylon separator with 0.45
.mu.m pores, squares (4) represent measurements made on a battery
having a nylon separator with 0.80 .mu.m pores, and diamonds (5)
represent measurements made on a battery having a glass microfiber
separator with 1.0 .mu.m pores. Each battery was assembled in a
2032 coin cell format and had an anode comprising an aluminum foil
treated with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, and the electrolyte was an
0.5 M aqueous aluminum nitrate solution. Polypropylene separators
(pentagons) were tested at 10 .mu.A/cm.sup.2 and 20 .mu.A/cm.sup.2;
mixed cellulose ester separators (triangle) and nylon separators
(circle) were tested at 20 .mu.A/cm.sup.2; nylon separators
(squares) were tested at 20 .mu.A/cm.sup.2, 40 .mu.A/cm.sup.2 and
50 .mu.A/cm.sup.2; and glass microfiber separators (diamonds) were
tested at 20 .mu.A/cm.sup.2 and 40 .mu.A/cm.sup.2.
[0034] FIG. 13 illustrates the discharge of a battery having a
polypropylene separator with 0.067 .mu.m pores at a current density
of 10 .mu.A/cm.sup.2. The battery was assembled in a 2032 coin cell
format and had an anode comprising an aluminum foil treated with
LiOH as described in Example 1, a cathode comprising acid-treated
lithium manganese oxide, and the electrolyte was an 0.5 M aqueous
aluminum nitrate solution.
[0035] FIG. 14 illustrates the discharge of a battery having a
nylon separator with 0.80 .mu.m pores at a current densities of 20
.mu.A/cm.sup.2 (curve 1), 40 .mu.A/cm.sup.2 (curve 2), and 40
.mu.A/cm.sup.2 (curve 3). The battery was assembled in a 2032 coin
cell format and had an anode comprising an aluminum foil treated
with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, and the electrolyte was an
0.5 M aqueous aluminum nitrate solution.
[0036] FIG. 15 illustrates the discharge of a battery having a
glass microfiber separator with 1.0 .mu.m pores at a current
densities of 20 .mu.A/cm.sup.2 (curve 1) and 40 .mu.A/cm.sup.2
(curve 2). The battery was assembled in a 2032 coin cell format and
had an anode comprising an aluminum foil treated with LiOH as
described in Example 1, a cathode comprising acid-treated lithium
manganese oxide, and the electrolyte was an 0.5 M aqueous aluminum
nitrate solution.
[0037] FIG. 16 is a photograph of the free-standing, translucent
solid polymer electrolyte measuring about 1 mm in thickness and
about 3 cm in diameter.
[0038] FIG. 17 illustrates the voltage profile of a battery having
a solid polymer electrolyte, showing a short duration of discharge
at 50 .mu.A/cm.sup.2, followed by discharging at 20 .mu.A/cm.sup.2
and charging at a current density of 20 .mu.A/cm.sup.2, with an
inset of a photograph of solid polymer electrolytes. The battery
was assembled in a 2032 coin cell format and had an anode
comprising an aluminum foil treated with LiOH as described in
Example 1, a cathode comprising acid-treated lithium manganese
oxide, and a 25 .mu.m thick polypropylene separator with an average
pore size of 0.067 The surface of the cathode was further treated
with 2 M LiOH prior to assembly and testing. The electrolyte was
prepared by mixing 6.7 weight % poly(vinylidene
fluoride-co-hexafluoropropylene) (PVDF-HFP), 20 weight % aluminum
nitrate and 10 weight % LiOH in 73.3 weight % deionized water. The
solution was then placed inside a furnace maintained at 120.degree.
C. overnight to remove the water content and obtain the resultant
solid polymer electrolyte.
[0039] FIG. 18 shows a discharge profile produced by a combination
of low-current and high-current pulses. The battery was assembled
in a 2032 coin cell format and had an anode comprising an aluminum
foil treated with LiOH as described in Example 1, a cathode
comprising acid-treated lithium manganese oxide, a 0.5 M aluminum
nitrate (aq) electrolyte and a 25 .mu.m thick polypropylene
separator with an average pore size of 0.067 The current densities
were switched between 100 A/g (low-current pulse) and 500 A/g
(high-current pulse), where the current is normalized with respect
to the mass of the cathode.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0040] The following non-limiting examples further illustrate the
various embodiments described herein.
[0041] The aluminum ion battery chemistry described in this
disclosure relies on simple electrode and aqueous electrolyte
chemistry and is based on the movement of hydroxyaluminates between
an aluminum anode source and a host cathode material. Incorporation
of aluminum anode and graphite or acid-treated lithium manganese
oxide cathode, along with an aqueous electrolyte comprising an
inexpensive aluminum salt ensures cost-competitiveness of the
technology. Aluminum is abundantly available and is inherently
safer and electrochemically more robust compared to lithium metal,
facilitating the use in aqueous environments as well as ambient
atmospheric conditions in a safe and reliable manner. Moreover, the
approach adopted here to incorporate hydrophilicity to
aluminum-based anodes is inexpensive and highly scalable. Both
carbon and lithium manganese oxide cathodes are easy to manufacture
and are considered to be extremely safe over a wide range of
operating conditions and are compatible with a wide range of
aqueous, non-aqueous, ionic and solid electrolytes, lending
flexibility and scalability to the battery technology. Moreover the
use of air stable electrodes and aqueous electrolytes is expected
to significantly reduce the time, cost and complexity of
manufacturing of the proposed aluminum ion aqueous battery relative
to other competing battery chemistries that rely on elaborate
manufacturing and assembly techniques, often in humidity-controlled
dry room environments. The preliminary performance parameters
indicate excellent reliability and repeatability. The estimated
volumetric and gravimetric energy density are about 30 Wh/L and 75
Wh/kg respectively for the aluminum-graphite system and 50 Wh/L and
150 Wh/kg respectively for the aluminum-acid-treated lithium
manganese oxide system, normalized with respect to the mass and
volume of cathode, thereby offering significant advancements over
alternate emerging battery technologies.
[0042] In general, multivalent ion transfer has been a holy grail
for battery technology. In the commercially available lithium ion
battery, an electron removed from lithium metal travels through the
external load while a corresponding single equivalent charged ion
is transferred between the anode and cathode of the battery through
the electrolyte. For a long time, efforts to increase energy
density have sought to transfer an equivalent ion between the
electrodes when multiple electrons are removed from an atom of a
metal such as magnesium, calcium, zinc, aluminum, manganese, or
vanadium. Such an approach has the potential to linearly scale
energy density in proportion to the number of electrons removed
from each atom. However, such efforts have not been successful, as
multivalent ions are inherently highly reactive and cannot be
successfully transported through the electrolyte to the counter
electrode. The present inventors have developed an innovative
solution to this challenging problem by transforming a multivalent
ion into a single monovalent ion which is much easier to transport
to the counter electrode. As disclosed herein, this concept is
broadly applicable across various types of multivalent ions. In the
disclosed embodiments, while three electrons are removed from an
aluminum atom, instead of carrying a single ion with equivalent
charge, the aluminum ion (Al.sup.3+) combines with hydroxides to
form a single ion with only a single charge (Al(OH).sub.4.sup.1-)
that is transported to the counter electrode. While not wishing to
be bound by theory, it is believed that this approach eliminates
the problem associated with the highly reactive multivalent ions
and yet has the ability to linearly scale the energy density when
multiple electrons are removed from a metal. In other embodiments,
a multivalent ion could be transformed into more than one type of
monovalent ions subject to the chemistry deployed. In further
embodiments, a multivalent ion, such as an ion of +3, can be
transformed into ions that are either monovalent or multivalent
type having reduced valence or combinations thereof.
[0043] As used herein, "aluminum" and "aluminium" are used
interchangeably to refer to the same element. "Aluminum" is the
preferred term that is used.
[0044] As used herein, "aluminum ion" includes polyatomic aluminum
anions, such as the hydroxyaluminate anion, Al(OH).sub.4.sup.1-,
the tetrachloroaluminate ion, AlCl.sub.4.sup.1-, the
tetrahydroaluminate ion, AlH.sub.4.sup.1-, and the
hexafluoroaluminate ion, AlF.sub.6.sup.1-.
[0045] As used herein, "delithiation" or "delithiated" refers to
the removal of lithium from a compound including lithium, such as
lithium manganese oxide, including removal by chemical methods,
such as acid treatment, electrochemical methods or a combination of
chemical and electrochemical methods. The product of the
delithiation of lithium manganese oxide can be expressed as
Li.sub.1-xMnO.sub.2, where x denotes the amount of lithium removed
by the delithiation method. As the delithiation method approaches
complete removal of lithium, x approaches 1, and the product is
substantially MnO.sub.2. In certain embodiments, the product is
substantially MnO.sub.2.
[0046] The next generation of energy storage technology should
therefore enable elimination of the aforementioned disadvantages
while simultaneously facilitating lower costs. A list of the
desirable attributes have been provided in Table 1, below. In
addition, the US Department of Energy has also specified four
specific challenges to large-scale deployment of energy storage for
grids: (1) cost-competitive technology, (2) validated reliability
and safety, (3) equitable regulatory environment, and (4) industry
acceptance.
TABLE-US-00001 TABLE 1 An overview of the desired attributes of
next generation battery systems and their potential impacts
Characteristic Impact High operating Fewer cells in series;
voltages Lower costs of implementation; Ability to integrate in a
wide range of applications including consumer electronics
Characteristic Simplified battery management voltage plateau
systems Simple electrode and Ease of manufacturing; electrolyte
components Enhanced safety; Lower cost Room temperature operation
Improved safety Minimal external accessories Easy maintenance;
(insulation, cooling, pumps, Lower cost storage tanks, etc.)
[0047] The aluminum-ion battery storage technology is based on the
movement of aluminum ions between an anode and a cathode, through
an aqueous electrolyte and a separator that is permeable to the
aluminum ions. In certain embodiments, the aluminum ions are
polyatomic aluminum anions. In certain embodiments, the separator
is a polymeric material. A porous, at least partially hydrophilic
polymer separator provides an insulating separation layer between
the anode and cathode, thereby preventing potential shorting
between the two electrodes. In certain embodiments, the polymer
separator is a polypropylene, cellulose ester or nylon separator.
The porosity of the separator is adapted to facilitate the movement
of the aluminum ions between the anode and cathode.
[0048] Aluminum electrochemistry has several advantages over the
other battery technologies that are available today. Aluminum has a
theoretical energy density of 1060 Wh/kg, compared to 406 Wh/kg of
lithium ions, due to the presence of three valence electrons in
aluminum as compared to one valence electron in lithium. Aluminum
is the third most abundant element (after oxygen and silicon), and
the most abundant metal available in the earth's crust (8.1 weight
%), compared to lithium (0.0017 weight %), sodium (2.3 weight %)
and vanadium (0.019 weight %), providing an opportunity to reduce
material costs. Finally, aluminum is both mechanically and
electrochemically robust and can be safely operated in ambient air
as well as humid environments while simultaneously facilitating a
greater flexibility in the choice of electrolytes (aqueous,
organic, ionic and solid) and operating conditions.
[0049] While aluminum is the preferred element, other
electrochemically active elements that form hydroxides that possess
sufficient ionic mobility and electrical conductivity may also be
used. Such elements include alkali metals such as lithium, sodium
and potassium, alkaline earth metals such as calcium and magnesium,
transition metals such as manganese, and post-transition metals
such as tin.
[0050] In certain embodiments, the electrolyte comprises an aqueous
solution of an aluminum salt. A preferred solvent is deionized
water. In certain embodiments, the aluminum salts include aluminum
nitrate, aluminum sulfate, aluminum phosphate, aluminum bromide
hexahydrate, aluminum fluoride, aluminum fluoride trihydrate,
aluminum iodide hexahydrate, aluminum perchlorate, aluminum
hydroxide, and combinations thereof. Preferred aluminum salts are
aluminum nitrate, aluminum bromide hexahydrate, aluminum fluoride,
aluminum iodide hexahydrate, and combinations thereof. In an
embodiment, the aluminum salt is aluminum nitrate.
[0051] In certain embodiments, the aluminum salt is present in an
aqueous solution of about 0.05 M to about 5.0 M. In some
embodiments, the aluminum salt is present in an aqueous solution of
about 0.5 M to about 3.0 M. In certain embodiments, the electrolyte
comprises about 0.1M to about 3.0 M sodium nitrate aqueous
solution. In certain preferred embodiments, the electrolyte
comprises about 1M to about 3.0 M sodium nitrate (aqueous).
[0052] One of ordinary skill would recognize that the aqueous
aluminum salt electrolyte is environmentally benign, non-toxic and
non-flammable and is therefore safer than organic electrolytes used
in commercial lithium ion batteries and many sodium ion batteries
today.
[0053] In certain embodiments, an anode comprises aluminum metal
foils. In preferred embodiments the aluminum metal foil has been
treated to increase its hydrophilic properties. In other
embodiments, an anode comprises an aluminum compound selected from
the group consisting of an aluminum transition metal oxide
(Al.sub.xM.sub.yO.sub.z, where M is a transition metal selected
from the group consisting of iron, vanadium, titanium, molybdenum,
copper, nickel, zinc, tungsten, manganese, chromium, cobalt and
mixtures thereof and x, y, and z range from 0 to 8, inclusive); an
aluminum transition metal sulfide, (Al.sub.xM.sub.yS.sub.z, where M
is a transition metal selected from the group consisting of iron,
vanadium, titanium, molybdenum, copper, nickel, zinc, tungsten,
manganese, chromium, cobalt and mixtures thereof and x, y, and z
range from 0 to 8, inclusive); aluminum lithium cobalt oxide
(AlLi.sub.3CoO.sub.2); lithium aluminum hydride (LiAlH.sub.4);
sodium aluminum hydride (NaAlH.sub.4); potassium aluminum fluoride
(KAlF.sub.4); and mixtures thereof.
[0054] In certain embodiments, an anode comprises an alloy of
aluminum and one or more metals selected from the group consisting
of lithium, sodium, potassium, manganese and magnesium and
combinations thereof. In certain embodiments, the anode comprises
an aluminum alloy comprising aluminum and at least one element
selected from the group consisting of manganese, magnesium,
lithium, zirconia, iron, cobalt, tungsten, vanadium, nickel,
copper, silicon, chromium, titanium, tin, zinc and combinations
thereof. The operating voltage in batteries that use carbon-based
cathodes could be increased through the incorporation of high
activation energy alloy anodes.
[0055] Improvement of cathode materials can be gained by
introduction of porosity and voids or modifications in the grain
structure and orientation within the existing graphite or
acid-treated lithium manganese oxide compositions. Such
improvements can provide a more efficient movement and storage of
larger charged ions in the discharge reaction, thereby increasing
the net capacity of the battery.
[0056] Alternatives to aluminum anodes, such as aluminum metal
sulfides and aluminum metal oxides can potentially offer higher
operating voltages, associated with the high activation energy of
such compounds. Moreover, such alternatives also facilitate the
incorporation of a mixed, hybrid-ion technology whereby the
capacity contribution is available from more than one metal ion,
thereby directly increasing the achievable capacities and hence,
available energy densities. Such alternatives to aluminum anodes
are also more stable over a wider range of operating parameters
such as mechanical stresses, high/low operating temperatures and
choice of electrolytes.
[0057] Examples of the chemical reactions associated with aluminum
metal oxides is provided below:
Al.sub.2CoO.sub.4.fwdarw.AlCoO.sub.4+Al.sup.3++3e (1)
[0058] Where cobalt changes its oxidation state from Co.sup.3+ to
Co.sup.5+ following the dissociation reaction of cobalt aluminate
and the release of one aluminum ion.
AlLi.sub.3CoO.sub.2.fwdarw.CoO.sub.2+Al.sup.3++3Li.sup.++6e
(2).
[0059] Cobalt changes its oxidation state from Co.sup.2+ to
Co.sup.4+ following the dissociation reaction and the release of
one aluminum ion and three lithium ions.
[0060] In embodiments using aluminum compounds comprising alkali
metals, the following reactions can be considered.
AlH.sub.4.sup.1-+Na.sup.1+.fwdarw.NaH+AlH.sub.3 (3).
AlF.sub.6.sup.3-+3Li.sup.1+.fwdarw.Li.sub.3F.sub.3AlF.sub.3
(4).
[0061] Aqueous electrolytes containing a dispersion of alternate
aluminum salts (such as sulfates, phosphates and perchlorates) can
effect changes in ionic mobility and operating voltages.
[0062] In addition to aqueous electrolytes, ionic electrolytes
offer the ability to achieve significantly higher operating
voltages (typically, >5 V), thereby increasing the achievable
energy density (defined as the product of charge storage and
operating voltage). Solid electrolytes, comprising aluminum and
aluminum-metal-based salts dispersed in polymers such as
polyethylene oxides are used in the disclosed aluminum ion battery
chemistry. Solid electrolytes are low cost alternatives to ionic
electrolytes that allow reasonably high operating voltages along
with a marked improvement in terms of ionic mobility.
[0063] In certain embodiments, the separator is a porous
polypropylene separator or a nylon membrane separator that provides
an insulating layer between the anode and cathode along and
provides sufficient porosity for the efficient transport of ions
between the two electrodes. In certain embodiments, the separator
comprises a porous polymer material selected to provide the needed
functionality at lesser expense, which can significantly drive down
the cost of the technology.
[0064] The onset, extent and impact of electrolysis within the
battery chemistry has been studied. The current set of operating
parameters rely on relatively low voltages at which electrolysis
will be absent or at the most, inconsequential. However, the choice
of electrodes and electrolytes bring in a sufficient degree of
thermodynamic non-ideality factor which can increase the
electrolysis voltage to as much as 1.8 V (instead of 1.23 V). Such
high operating voltages with aqueous electrolytes not only enable
higher capacities but can also lead to the introduction of
additional reaction mechanisms which were otherwise unavailable at
voltages less than 1.2 V. In terms of hybrid ion battery
chemistries, higher operating voltage can also introduce the
involvement of multiple metal ions such as lithium ions from the
lithium manganese oxide cathode. Further studies throughout an
entire range of operating parameters to determine the
characteristic responses of the battery technology.
[0065] Cathode Materials. Two cathode materials were studied in
working examples: acid-treated lithium manganese oxide and
graphite-graphite oxide composite. A suitable cathode material
should have sufficient porosity and inter-sheet voids to
accommodate the insertion and intercalation of large polyatomic
aluminum anions. The cathode material should also be partially
hydrophilic for wettability with an aqueous electrolyte. These two
cathode materials meet these criteria, but other materials, notably
graphene and manganese dioxide, could also meet these criteria.
[0066] Pristine graphite cathodes do not typically provide large
inter-sheet voids and porosity or hydrophilicity. While oxygen
plasma treated graphite could improve the hydrophilicity of the
cathode material, there is an issue of whether inter-sheet voids
would accommodate large polyatomic aluminum anions.
[0067] The spinel structure of lithium manganese oxide provides
hydrophilicity as well as porosity and inter-sheet voids suitable
for accommodating large polyatomic aluminum anions. Similarly,
graphite-graphite oxide composites were found to be suitable
cathode materials for the proposed aluminum-ion chemistry, owing to
the hydrophilicity and large inter-sheet voids introduced by the
oxygen atoms.
[0068] One of ordinary skill would recognize that graphene also has
sufficiently large inter-sheet voids, owing to the precursor
graphene oxide material, which is subsequently reduced to increase
conductivity and form graphene. However, graphene is inherently
hydrophobic and therefore, graphene sheets need to be exposed to
oxygen plasma to introduce oxygen containing species and improve
hydrophilicity. Additional alternate cathode materials capable of
accommodating the diffusion and storage of large aluminum-based
ions, such as manganese dioxide, are being studied to evaluate on
the cost, porosity and inter-sheet voids of the potential
materials.
[0069] Lithium manganese oxide materials can be improved by
leaching lithium atoms from the lithium manganese oxide materials
through treatment with acids. When the lithium manganese oxide
material is treated with a mineral acid such as nitric acid or
hydrochloride acid, the lithium atoms are removed in the form of
the corresponding lithium nitrates or lithium chlorides, thereby
creating additional voids within the cathode structure. Suitable
acids include aqueous solutions of 10%-90% nitric, hydrochloric,
sulfuric, acetic, hydroiodic, or phosphoric acid. In one
embodiment, lithium atoms can be removed by dispersing lithium
manganese oxide in an acidic medium (30%-70% concentrated
hydrochloric or nitric acids) and sonicated for 1-6 hours until a
stable dispersion is obtained. If nitric acid is used the color of
the lithium manganese oxide changes from black to dark red. In
another embodiment, lithium atoms can be removed by stirring the
suspension of dispersing lithium manganese oxide in an acidic
medium at room temperature for about 0.5 to about 6 hours,
typically about two hours. In other embodiments, the suspensions
were stirred for various durations from 0.5 hours to 24 hours at
different temperatures from room temperature to about 80.degree. C.
The resulting suspension is then filtered through a filter membrane
with pore size ranging from 0.1-40 .mu.m, preferably with a pore
size greater than 0.2 .mu.m and is repeatedly washed with deionized
water or ethanol to remove trace amounts of residues, such as
LiNO.sub.3. Suitable filter membrane materials, such as nylon, are
those that can withstand the acid used in the process. The filtrate
is then dried in a vacuum furnace to obtain the resultant powder,
Li.sub.1-xMnO.sub.2, where x denotes the amount of lithium removed
by the acid treatment process. As the acid treatment approaches
complete removal of lithium, x approaches 1, and the product is
substantially MnO.sub.2.
[0070] In certain embodiments, commercially available lithium
manganese oxide is dispersed in 30% concentrated hydrochloric acid
or 67% concentrated nitric acid and sonicated for six hours until a
stable dispersion is obtained. Formation of a dispersion is
indicated by a change in color from black to reddish brown. The
resulting suspension is then filtered through a Whatman nylon
membrane filter with pore size ranging from 0.2-0.45 .mu.m and is
repeatedly washed to remove trace amounts of the acid. The filtrate
is then dried in a vacuum furnace at 110.degree. C. to obtain the
resultant powder, Li.sub.1-xMnO.sub.2.
[0071] Batteries were fabricated that used the aluminum based
electrochemistry, including an aluminum anode and an aqueous
solution of an aluminum salt as an electrolyte. In certain
embodiments, batteries contained an aluminum anode, an acid-treated
lithium manganese oxide cathode and an aqueous solution of an
aluminum salt as an electrolyte in a coin cell configuration. In
certain embodiments, batteries contained an aluminum anode, a
graphite-graphite oxide composite cathode and an aqueous solution
of an aluminum salt as an electrolyte in a coin cell configuration.
In certain embodiments, batteries contained an aluminum anode, a
graphene cathode and an aqueous solution of an aluminum salt as an
electrolyte in a coin cell configuration. When a 1 M aqueous
solution of aluminum nitrate was used as the electrolyte, the
batteries having an aluminum anode and an acid-treated lithium
manganese oxide cathode chemistry provided an open circuit voltage
of about 1 volt. When a 1 M aqueous solution of aluminum nitrate
was used as the electrolyte, the batteries having an aluminum anode
and graphite-graphite oxide composite cathode provided an open
circuit voltage between 600 mV and 800 mV. When a 1 M aqueous
solution of aluminum nitrate was used as the electrolyte, the
batteries having an aluminum anode and a graphene cathode provided
an open circuit voltage between 600 mV and 800 mV. When the cells
were discharged, aluminum-based ions migrated from the anode
towards the cathode. Following a discharge, when the cells were
charged, aluminum ions migrated to the anode.
WORKING EXAMPLES
Example 1
Alkali Metal Hydroxide Treatment of the Aluminum Anode
[0072] Battery-grade pristine aluminum foils were treated to
increase hydrophilicity and improve wettability of the anode. While
not wishing to be bound by theory, it is believed that a
hydrophobic aluminum anode would prevent efficient ion transport
due to high interfacial resistance between the aluminum metal and
aqueous electrolyte interface, leading to a significant drop in
performance. The hydrophilicity of the surface of the aluminum
metal was increased by treatment with a lithium hydroxide aqueous
solution. Lithium is known to have a strong affinity for aluminum,
forming a range of lithium-aluminum based alloys, characterized by
the formation of a greyish-white texture on the aluminum surface.
The resulting aluminum anode is found to be significantly more
hydrophilic than untreated, pristine aluminum. Aqueous solutions of
other alkali metal hydroxides, such as sodium hydroxide and
potassium hydroxide, are also suitable for use in this
treatment.
[0073] FIG. 1A is a photograph of a piece of aluminum foil treated
with a drop of 1 M aqueous solution of lithium hydroxide; FIG. 1B
is a photograph of the piece of the treated aluminum foil of FIG.
1A showing a change in the appearance of the drop of the aqueous
solution of lithium hydroxide. After a short time the aqueous
solution of lithium hydroxide was wiped away and the surface of the
aluminum foil was allowed to air dry at room temperature
(25.degree. C.). Reaction times of 5-10 seconds to 1 hour have been
tested, but the reaction appears to be complete in 5-10 seconds.
FIG. 1C is a photograph of the piece of treated aluminum foil of
FIG. 1B showing the greyish-white appearance of the aluminum foil
following the drying of the lithium hydroxide solution. FIG. 1D is
a photograph of the piece of treated aluminum foil of FIG. 1C
showing the effect of placing a drop of deionized water on the
treated aluminum foil, indicating an increase in hydrophilicity of
the treated aluminum foil. FIG. 1E is a photograph of a drop of
deionized water on untreated aluminum foil for comparison to FIG.
1D. In certain embodiments, an aqueous solution of about 0.01M to
about 5.5M lithium hydroxide can be used.
[0074] Other means of increasing the hydrophilicity of an aluminum
metal surface, such as nitrogen and oxygen plasma and treatment
using acid-based treatments, primarily rely on the introduction of
hydrophilic native aluminum oxide layers on the metal surface.
Acid-based treatments involve complicated chemistry, increasing
manufacturing costs, and have significant environmental impacts
associated with use and disposal. Plasma treatment, on the other
hand, is an expensive high voltage process, and is unsuitable for
large-scale manufacturing.
Example 2
Aluminum Anode Vs. Acid-Treated Lithium Manganese Oxide Cathode
Battery and Aluminum Anode Vs. Graphite-Graphic Oxide Cathode
Battery
[0075] Batteries were assembled using an aluminum anode, an
acid-treated lithium manganese oxide cathode and an aqueous
solution of aluminum nitrate as the electrolyte. Studies were
conducted using the standard 2032 coin cell form factor,
illustrated in FIG. 2. FIG. 2 is a schematic diagram of an exploded
view of a test battery 100 in a coin cell format, showing the
positive case 110, a spring 120, a first spacer 130, a cathode 140,
a separator 150, an anode 160, a second spacer 170 and the negative
case 180. Prior to assembly of the test battery 100, aliquots of
the electrolyte are placed between the separator 150 and the anode
160, as well between the separator 150 and the cathode 140.
Preferably, the first spacer 130, the cathode 140, the separator
150, the anode 160, and the second spacer 170 are immersed in and
equilibrated with the electrolyte prior to assembly of the test
battery.
[0076] A battery grade aluminum foil is used as the anode 160.
Battery grade foils are generally >99% pure. The thickness of
any battery-grade foil should be limited, since the thickness
directly impacts the volumetric energy density at the system level,
defined as: (Net Available Energy Density in Watt-hours/Total
volume of the electrode, including the current collector). Thicker
current collectors also reduce the maximum number of electrodes
that can be stacked in a battery pack/module. Ideally,
battery-grade current collectors vary between 8-30 .mu.m in
thickness. Mechanical robustness is also necessary to prevent any
wear and tear during the electrode coating or cell/battery assembly
process. The tensile strength of commercial battery-grade foils
vary between 100-500 N/mm. Suitable battery grade aluminum foil and
other materials may be obtained from MTI Corporation, Richmond,
Calif. and Targray Technology International Inc., Laguna Niguel,
Calif. Battery grade lithium manganese oxide cathode and graphite
may be obtained from MTI Corporation, Richmond, Calif. and Sigma
Aldrich, St. Louis, Mo. Graphene and graphite oxide may be
purchased from Sigma Aldrich, St. Louis, Mo., Graphene Supermarket,
Calverton, N.Y., and ACS Material, Medford, Mass.
[0077] Aluminum foil anodes were treated as described in Example 1
to improve their hydrophilic properties.
[0078] The charge/discharge steps were carried out in the voltage
window of 0-2V. As the cell was discharged, hydroxyaluminate
(Al(OH).sub.4.sup.-) ions were formed according to chemical
reaction (5):
Al.sup.3++4OH.sup.-.fwdarw.Al(OH).sub.4.sup.- (5)
[0079] The hydroxyaluminate ions migrate towards the cathode,
passing through the porous membrane separator.
[0080] At the cathode, the hydroxyaluminate ions diffuse through
the pores and inter-sheet voids of the cathode material and are
oxidized to give Al(OH).sub.3 (aluminum hydroxide). The presence of
aluminum hydroxide on the aluminum foil anode of a completely
(100%) discharged test cell has been confirmed using x-ray
photoelectron spectroscopy (XPS), as shown in FIG. 3. The XPS
profile shows one major Al 2p transition at 74.3 eV, indicating the
presence of gibbsite, Al(OH).sub.3 on the anode. The transition at
74.3 eV has been reported to be characteristic of gibbsite by
Kloprogge et al. Kloprogge, J. T., et al., XPS study of the major
minerals in bauxite: gibbsite, bayerite and (pseudo-) boehmite,
Journal of Colloid and Interface Science, 2006, 296(2), 572-576. In
the reverse charging process, aluminum hydroxide is reduced at the
cathode and the aluminum ions migrate back to the anode.
[0081] The discharge and charge reactions at the cathode, chemical
reactions (6) and (7), respectively, are provided below:
Discharge,Al(OH).sub.4.sup.-.fwdarw.Al(OH).sub.3+OH.sup.++3e
(6);
Charge,Al(OH).sub.3+3e.sup.-.fwdarw.Al.sup.3++3OH.sup.- (7).
[0082] During the charging process, an additional contribution may
be observed at the acid-treated lithium manganese oxide cathode
through the dissociation reaction of lithium manganese oxide
according to reaction (8), below:
LiMnO.sub.2+e.sup.-.fwdarw.Li.sup.++MnO.sub.2 (8).
[0083] The lithium ions would then flow towards the aluminum anode
and possibly intercalate with aluminum, owing to the high affinity
between lithium and aluminum, forming a hybrid-ion battery
chemistry. This hypothesis could relate to an observed increase in
capacity (about 40%) compared to the capacities obtained with
carbon-based cathodes devoid of any lithium component. However, XPS
examination of the aluminum anode in a test cell having a lithium
manganese oxide cathode did not show any significant signs of
lithium-based alloys at the anode site at a fully charged state.
However, this result can be attributed to the fact that the
dissociation reaction of lithium manganese oxide occurs at
significantly higher voltages (>3V) and in the given voltage
window, the concentration of lithium ions is negligible compared to
the presence of aluminum-based alloys. In addition, XPS is a
surface-based analytic technique and the excellent lithium ion
diffusion in aluminum might have caused the lithium ions to have
diffused within the bulk aluminum anode and would therefore be
absent from the surface.
[0084] Operating Parameters and Performance Metrics. The
aluminum-ion cells were cycled between safe voltage cut-off limits
of 0 V (discharge) and 2 V (charge). However, the average operating
voltage was about 1.1 V for discharge and 1.2 V for charge for the
cells having an aluminum anode and an acid-treated lithium
manganese oxide cathode (FIG. 4A) and 0.4 V for discharge and 0.9 V
for charge for the cells having an aluminum anode and a
graphite-graphite oxide cathode (FIG. 4B), within the safe voltage
cut-off limits.
[0085] FIG. 4A shows the voltage profile that was produced by
applying current at a current density of 0.1 mA/cm.sup.2 to a test
battery having an anode comprising an aluminum foil treated with
LiOH as described in Example 1, a cathode comprising acid-treated
lithium manganese oxide, a 25 .mu.m thick polypropylene separator
with an average pore size of 0.067 .mu.m, and a 0.5 M aqueous
aluminum nitrate electrolyte. FIG. 4B shows the voltage profile
that was produced by applying current at a current density of 0.1
mA/cm.sup.2 to a test battery having an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising graphite-graphite oxide, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 .mu.m,
and a 0.5 M aqueous aluminum nitrate electrolyte. The observed
average operating voltage is significantly higher with the use of
acid-treated lithium manganese oxide cathodes, possibly owing to
the higher activation energy for diffusion and intercalation of
ions. Carbon is known to possess a sufficiently low activation
energy for diffusion and intercalation of metal ions (the
intercalation voltage of lithium ions in carbon against a lithium
metal occurs at about 100 mV).
[0086] Moreover, the voltage profile demonstrates a characteristic
voltage plateau (FIG. 4A), unlike the voltage profiles observed in
sodium ion batteries, enabling critical advantages such as
incorporation of simpler battery management systems and
installation of fewer cells in series owing to the high operating
voltages, all of which can significantly drive down the cost of the
technology. The charge/discharge rates were limited between C/1 and
C/12 (a rate of C/n implies charge or discharge in n hours). While
cycle life testing is currently underway, both the graphite-based
and acid-treated lithium manganese oxide-based configurations have
so far demonstrated impressive cycle life, delivering close to
about 100% coulombic efficiency (defined as the ratio of charge to
discharge capacities and is indicative of irreversibility and
side-reactions in a battery chemistry). FIG. 5A shows the battery
charge capacity, open triangles, and discharge capacity, open
circles, as a function of the cycle index of a battery having an
anode comprising an aluminum foil treated with LiOH as described in
Example 1, a 25 .mu.m thick polypropylene separator with an average
pore size of 0.067 and a 0.5 M aqueous aluminum nitrate electrolyte
and a graphite-graphite oxide composite cathode. The coulombic
efficiency was estimated to be close to 100% over 30
charge/discharge cycles, indicating efficient and reversible charge
and discharge kinetics.
[0087] FIG. 5B shows the battery charge capacity as a function of
cycle index of a battery having an anode comprising an aluminum
foil treated with LiOH as described in Example 1, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 and a
0.5 M aqueous aluminum nitrate electrolyte and an acid-treated
Li.sub.1-xMnO.sub.2 cathode. The reduction in capacity after over
800 charge/discharge cycles is about 3% of the original
capacity.
[0088] Understandably, the acid-treated lithium manganese
oxide-aluminum chemistry with an aqueous electrolyte provides
higher energy density (about 100-150 Wh/kg) and volumetric energy
density (about 30-60 Wh/L) than the graphite-graphite
oxide-aluminum chemistry (about 50-75 Wh/kg and about 20-30 Wh/L),
normalized by the mass and volume of cathode, owing to the higher
electrochemical affinity towards aluminum observed in acid-treated
lithium manganese oxide. However, graphite-graphite oxide cathodes
are generally cheaper than lithium manganese oxide. Further
modifications to the cathode chemistry may significantly boost the
performance metrics of graphite-graphite oxide cathodes.
[0089] Sequential cyclic voltammetry tests were carried out to
measure the ion diffusion coefficient in batteries having an anode
comprising an aluminum foil treated with LiOH as described in
Example 1, a 25 .mu.m thick polypropylene separator with an average
pore size of 0.067 .mu.m, and a 0.5 M aqueous aluminum nitrate
electrolyte and an acid-treated lithium manganese oxide cathode
(FIG. 6A) or batteries having an anode comprising an aluminum foil
treated with LiOH as described in Example 1, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 .mu.m,
and a 0.5 M aqueous aluminum nitrate electrolyte and
graphite-graphite oxide composite cathode (FIG. 6B). The test
batteries in the coin cell format were cycled at various voltage
sweep rates between 10 mV/sec and 50 mV/sec within a voltage range
of 0 V and 1.5 V.
[0090] The diffusion coefficient was calculated using Fick's law
following equation (I):
.differential. C .differential. t = D .differential. 2 C
.differential. r 2 + 2 D r .times. .differential. C .differential.
r . ( I ) ##EQU00001##
[0091] The response of current can then be obtained as:
i = nFADC R 0 + nFAD 1 / 2 C .pi. 1 / 2 t 1 / 2 . ( II )
##EQU00002##
[0092] Where n is the number of electrons exchanged, F is Faraday's
constant, A is the area of the electrode, D is the diffusion
coefficient, C is the molar concentration, t is time for diffusion
and R.sub.0 is the radius of the cathode particles.
[0093] The current response can be simplified and re-written
as:
i=kt.sup.1/2+b (III),
[0094] where
b = nFADC R 0 ( IV , V ) k = nFAD 1 / 2 C .pi. 1 / 2 , or , D = b 2
R 0 2 .pi. k 2 . ( VI ) ##EQU00003##
[0095] Subsequently, the diffusion coefficient of hydroxyaluminate
ions in acid-treated lithium manganese oxide and graphite-graphite
oxide composite cathodes was calculated to be 1.14.times.10.sup.-7
cm.sup.2/sec and 3.54.times.10.sup.-8 cm.sup.2/sec respectively,
well within the acceptable range of ion diffusion coefficients in
metal-ion batteries.
[0096] In addition, electrochemical impedance spectroscopy (EIS)
was carried out to analyze the internal resistances of batteries
having an anode comprising an aluminum foil treated with LiOH as
described in Example 1, a 25 .mu.m thick polypropylene separator
with an average pore size of 0.067 .mu.m, and a 0.5 M aqueous
aluminum nitrate electrolyte and an acid-treated lithium manganese
oxide cathode (FIG. 7A) and batteries having an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a 25
.mu.m thick polypropylene separator with an average pore size of
0.067 .mu.m, and a 0.5 M aqueous aluminum nitrate electrolyte and a
graphite-graphite oxide cathode (FIG. 7B). Insets show the Randles
equivalent circuit used to fit the spectra.
[0097] Since the operating voltages are close to the electrolysis
voltage of the aqueous electrolyte system, analyzing EIS is
critical to understand potential safety threats associated with gas
evolution inside the cell. It is understood that the evolution and
presence of gas pockets (H.sub.2 and O.sub.2) within the
electrolyte will directly increase the electrolytic resistance
while the evolution of these gases at the electrode-electrolyte
interface will increase the interfacial resistance.
[0098] The EIS profile was fitted with a Randles equivalent circuit
model and the electrolytic resistance, interfacial resistance and
charge transfer resistances, summarized in Table 2, below, were
estimated based on the fit. The electrolytic resistances were
estimated to be between 2-4.OMEGA., significantly lower than the
typical electrolytic resistances of 10-20.OMEGA., consistent with
the absence of any gas pockets within the electrolyte. The
interfacial resistance was estimated to be 11.OMEGA. at the
acid-treated lithium manganese oxide-electrolyte interface and
20.OMEGA. at the graphite-graphite oxide-electrolyte interface,
again consistent with the absence of any insulating gas pockets.
The charge transfer resistance of acid-treated lithium manganese
oxide was estimated to be about 100.OMEGA. while that of
graphite-graphite oxide composite was estimated to be slightly
higher at about 131.OMEGA., possibly attributed to the presence of
oxygen-containing functional groups. Charge transfer resistance is
indicative of the electron conductivity of the active electrode
material and is independent of the formation of gas pockets. One of
ordinary skill would recognize that a charge-transfer resistance of
100-150.OMEGA. is generally considered to be suitable for battery
storage applications.
TABLE-US-00002 TABLE 2 EIS Profile Results Acid-Treated Lithium
Graphite-Graphite Parameter Manganese Oxide Cathode Oxide Cathode
Rel 2-4 .OMEGA. 2-4 .OMEGA. Rint 11 .OMEGA. 20 .OMEGA. Rct about
100 .OMEGA. about 131 .OMEGA.
[0099] In order to assess form factor scalability of the aluminum
ion battery chemistry, pouch cell and prismatic cells were also
assembled and tested. A schematic depiction of the prismatic cell
assembly is provided in FIG. 8A. The prismatic assembly 80
comprised a metallic or a polymer base plate 82 an insulating
polymer gasket 84 and a top plate resembling the structure of the
base plate, not shown for clarity. The components had threaded
through-holes along its edges. For metallic base and top plates,
nylon screws were used to seal the assembly while simultaneously
preventing a shorting between the two plates while for polymer base
and top plates, both nylon and metallic screws sufficed. A
prismatic cell was assembled with an electrode area of 2 cm.times.5
cm and rated at a capacity of 1 mAh. Standard polypropylene
separators were used in the assembly. The cell comprised a single
interface, although multiple interfaces can also be incorporated
with the setup.
[0100] FIG. 8B illustrates the discharge voltage profile of a
prismatic cell rated at 1 mAh. The cell had an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising acid-treated lithium manganese oxide, a 25 .mu.m
thick polypropylene separator with an average pore size of 0.067
.mu.m, 0.5 M aqueous aluminum nitrate electrolyte and were tested
at 10 .mu.A/cm.sup.2.
[0101] Pouch cells were assembled by introducing the
anode-separator-cathode interface in the cell assembly section of
an aluminum laminate pouch cell packaging case. This was followed
by connecting the electrodes to an aluminum current collector tab
through mechanical contacts or ultrasonic welding. Next, three
edges of the pouch cell were sealed using a heat sealer set between
about 20-50 psi and 150-180.degree. C. A section of the pouch cell
was retained at one of the edges that acted as the gas trap. The
purpose of the gas trap is to contain the gas evolution during the
formation cycle, after which the gas trap section can be cut and
the edge resealed for subsequent cycling. Prior to sealing the
fourth and final edge of the pouch cell, the electrodes-separator
assembly was wetted with the electrolyte. The fourth edge is sealed
in a vacuum sealing furnace with the vacuum set at about -90 psi.
The pressure and temperature parameters are unchanged and are set
between 20-50 psi and 150-180.degree. C. respectively. A schematic
diagram of a pouch cell 90 is provided in FIG. 9A, showing a cell
assembly section 92, a gas trap 94 and current collector terminals
96. A pouch cell assembled in this fashion involved electrodes
between 1 cm.times.0.8 cm and 1 cm.times.1 cm, rated between
0.06-0.08 mAh.
[0102] FIG. 9B illustrates the discharge profile of a pouch cell
comprising 0.8 cm.times.1 cm electrodes and hydrophilic
polypropylene separators. The cell had an anode comprising an
aluminum foil treated with LiOH as described in Example 1, a
cathode comprising acid-treated lithium manganese oxide, a 25 .mu.m
thick polypropylene separator with an average pore size of 0.067
.mu.m, 0.5 M aqueous aluminum nitrate electrolyte and were tested
at about 25 .mu.A/cm.sup.2. Like the prismatic cell format, a pouch
cell assembled in this fashion can also incorporate scalability and
multiple interfaces can be packed in series/parallel configurations
to achieve a pre-determined capacity and voltage rating.
[0103] The need to find an alternate energy storage system to meet
the ever-increasing demands from various sectors such as consumer
electronics, military, automotive and grid storage have continued
to rise exponentially in the last decade. While lithium ion
batteries are ubiquitous today in consumer electronics, its
limitations with respect to high costs and potentially hazardous
safety threats have limited its entry in emerging fields such as
grid storage, and automotive applications. Sodium ion batteries on
the other hand may offer a marginal reduction in the cost at the
system level but are significantly limited in performance metrics
in terms of available capacities and energy density, voltage window
and the choice of electrolytes. Alternate upcoming technologies
such as flow batteries and liquid metal batteries are still in
early stages of development. Moreover, such technologies pose
additional challenges in terms of cost of implementation and
safety. For instance, the availability of unlimited capacity in
vanadium redox flow batteries rely on large storage tanks and
industrial pumps that add to the cost and maintenance of the
battery system. Liquid metal batteries operate at very high
temperatures and incorporate the use of toxic materials such as
antimony and lead as well as flammable lithium metal, thereby
posing serious safety concerns.
[0104] Also disclosed are systems and methods of using the
disclosed rechargeable battery. FIG. 8 is a block diagram of an
embodiment of a system 800 that incorporates the battery 810 of the
present disclosure, showing a controller 820 that is operatively
connected to battery 810, a source of electrical power 830, a local
electrical load 840 and an electrical power distribution grid 850.
In certain embodiments, the source of electrical power 830 is based
on a renewable energy source, that is, a wind turbine or a solar
panel. The controller 820 is operatively connected to the source of
electrical power 830 and to the battery 810 of the present
disclosure to mediate the charging of the battery 810. The
controller 820 is operatively connected to the source of one or
more local electrical loads 840 and to the battery 810 of the
present disclosure to mediate the discharging of the battery 810.
The local electrical loads 840 can include devices requiring DC
electrical supply or AC electrical supply, including, without
limitation, cell phone or computer battery chargers, computers,
home appliances, water pumps, and refrigeration equipment. In
certain embodiments, the controller 820 is operatively connected to
a power distribution grid 850 to permit selling excess electrical
power to the power distribution grid 850.
Example 3
Electrolyte Additives
[0105] In some examples, the electrolyte, 0.5 M Al(NO.sub.3).sub.3,
was mixed with 10-50 vol. % 2 M LiOH to obtain a composite
electrolyte. While not wishing to be bound by theory, it is
believed that addition of LiOH to the electrolyte comprising
aluminum ions increases the concentration of OH.sup.-1 in the
electrolyte, and therefore prevents loss of active ions during
transportation through undesired side reactions. Owing to the
reactivity of aluminum in water, it is not uncommon to observe
oxidation of Al(OH).sub.4.sup.1- ions prior to reaction at the
cathode site.
[0106] The oxidation reaction can be summarized as:
Al(OH).sub.4.sup.1-.fwdarw.Al.sup.3++4OH.sup.-1 (9).
[0107] Depending on the concentration of OH.sup.-1 ions in the
electrolyte, there can be a reduction of active hydroxyaluminate
ions reaching the cathode, through a dissociation reaction that
subsequently leads to the oxidation of hydroxyaluminate and
re-formation of multivalent aluminum ions. Increasing the
concentration of OH.sup.-1 ions through incorporation of 2 M LiOH
in the electrolyte would shift the equilibration of the reaction to
favor Al(OH).sub.4.sup.1- ions over the dissociation to
Al.sup.3++4OH.sup.-1.
[0108] FIG. 11 compares the discharge and charging properties of
two batteries differing in electrolyte composition: one battery
having a 0.5 M Al(NO.sub.3).sub.3 (aq) electrolyte (curve 1) and
another battery having a 0.5 M Al(NO.sub.3).sub.3 and 2 M LiOH (aq)
electrolyte (curve 2). Each battery was assembled in a 2032 coin
cell format and had an anode comprising an aluminum foil treated
with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, a 25 .mu.m thick
polypropylene separator with an average pore size of 0.067 .mu.m,
and was tested at current densities of 10 .mu.A/cm.sup.2. In
certain embodiments, the electrolyte is an aqueous solution of
aluminum nitrate and lithium hydroxide in a molar ratio of about
1:1 to about 1:10.
[0109] The results illustrated in FIG. 11 suggest that
incorporation of a composite electrolyte can result in a reduced
over-potential. Incorporation of LiOH in the electrolyte reduces
the over-potential by preventing loss of active Al-ion species
during transportation in the electrolyte. The over-potential
relates to the discharge voltage hysteresis caused by the cell
composition. The voltage hysteresis during discharge is defined as
the change from the expected operating voltage attributed to
internal cell resistances and is conveyed through the equation
.DELTA.V=IR (where, .DELTA.V is the change in voltage, I is the
current and R is the internal resistance). The new operating
voltage, Vop', is then defined as Vop'=Vop-.DELTA.V. In FIG. 11,
curve 1, in which the electrolyte is 0.5 M (aq) Al(NO.sub.3).sub.3
with no LiOH additive, the higher internal resistances cause an
increase in the .DELTA.V value (which is known as the
over-potential), causing it to discharge at a lower voltage. In
contrast, the battery having an electrolyte that is 0.5 M
Al(NO.sub.3).sub.3 and 2 M LiOH aqueous solution (curve 2) has a
reduced internal cell resistance, therefore causing the .DELTA.V
value to be less than that of the battery of curve 1, resulting in
a higher discharge potential (which implies higher energy density,
since energy density=capacity.times.operating voltage)
[0110] While the example describes a LiOH--Al(NO.sub.3).sub.3
composite electrolyte, other hydroxide-containing compounds may
also be introduced into the electrolyte to achieve similar effects.
Some alternate electrolytic additives include hydroxides of sodium,
potassium, ammonium, calcium and magnesium. Since the alkali metal
ion (Li+, Na+ or K+ for example) is present only in the electrolyte
and has a polarity opposite to Al(OH).sub.4.sup.1- ions, it will
not contribute to discharge capacities.
Example 4
Separators
[0111] The aluminum ion chemistry disclosed herein involves the
transport of large Al(OH).sub.4.sup.1- ions. Therefore, the pore
size of the separator can dictate the ion transportation kinetics.
Standard batteries such as lithium ion batteries generally use a
polypropylene separator with pore sizes less than 0.1 .mu.m, which
is sufficient to permit the flow of the relatively smaller lithium
ions. However, as the size of the ions increase, as is the case
with Al(OH).sub.4.sup.1-, small pore sizes hinder the efficient
flow of ions, resulting in an increased internal cell resistance
and lower charging rate and discharging rate. Therefore, in an
effort to reduce accumulation of charge and resistance build-up at
the separator surface, batteries having separators with larger pore
diameters were studied.
[0112] The separators that were tested included polypropylene
separators (standard, 0.067 .mu.m pore size; Celgard LLC,
Charlotte, N.C.), mixed cellulose ester separators (0.2 .mu.m pore
size, Whatman), nylon separators (0.45 .mu.m, 0.8 .mu.m, 1.2 .mu.m
pore sizes, Whatman), and glass microfiber separators (1 .mu.m pore
size, Whatman). In general, larger pore sizes, including 0.8 .mu.m
and 1.2 .mu.m, permitted faster ion-transfer kinetics and better
rate capabilities compared to the smaller pore sizes. However as
the pore sizes were further increased, it appeared that there was
an increase in shorting of the anode and cathode that was
noticeable at a pore diameter of 2.7 .mu.m.
[0113] FIG. 12 illustrates the effect of separator pore size on the
average discharge potential produced at a given current density,
where pentagons (1) represent measurements made on a battery having
a polypropylene separator with 0.067 .mu.m pores, a triangle (2)
represents measurements made on a battery having a mixed cellulose
ester separator with 0.20 .mu.m pores, a circle (3) represents
measurements made on a battery having a nylon separator with 0.45
.mu.m pores, squares (4) represent measurements made on a battery
having a nylon separator with 0.80 .mu.m pores, and diamonds (5)
represent measurements made on a battery having a glass microfiber
separator with 1.0 .mu.m pores. Each battery was assembled in a
2032 coin cell format and had an anode comprising an aluminum foil
treated with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, and the electrolyte was an
0.5 M aqueous aluminum nitrate solution. Polypropylene separators
(pentagons) were tested at 10 .mu.A/cm.sup.2 and 20 .mu.A/cm.sup.2;
mixed cellulose ester separators (triangle) and nylon separators
(circle) were tested at 20 .mu.A/cm.sup.2; nylon separators
(squares) were tested at 20 .mu.A/cm.sup.2, 40 .mu.A/cm.sup.2 and
50 .mu.A/cm.sup.2; and glass microfiber separators (diamonds) were
tested at 20 .mu.A/cm.sup.2 and 40 .mu.A/cm.sup.2.
[0114] The pore size of the separators can also influence
suitability of a battery for an intended application.
Understandably, separators with larger pore sizes are also thicker
than those with smaller pore sizes. Therefore, while the range of
optimum pore sizes is rather large, a specific choice can be made
based on the intended application. For example, smaller pore sizes
(example, polypropylene, 0.067 .mu.m pore diameter and 25 .mu.m
thick) can optimize energy density (volumetric and gravimetric)
while larger pore sizes (example, glass microfiber, 1 .mu.m pore
diameter and 500 .mu.m thick) can optimize rate capability and
hence, improve the power density of such batteries.
[0115] FIG. 13 illustrates the discharge of a battery having a
polypropylene separator with 0.067 .mu.m pores at a current density
of 10 .mu.A/cm.sup.2. The battery was assembled in a 2032 coin cell
format and had an anode comprising an aluminum foil treated with
LiOH as described in Example 1, a cathode comprising acid-treated
lithium manganese oxide, and the electrolyte was an 0.5 M aqueous
aluminum nitrate solution.
[0116] FIG. 14 illustrates the discharge of a battery having a
nylon separator with 0.80 .mu.m pores at a current densities of 20
.mu.A/cm.sup.2 (curve 1), 40 .mu.A/cm.sup.2 (curve 2), and 40
.mu.A/cm.sup.2 (curve 3). The battery was assembled in a 2032 coin
cell format and had an anode comprising an aluminum foil treated
with LiOH as described in Example 1, a cathode comprising
acid-treated lithium manganese oxide, and the electrolyte was an
0.5 M aqueous aluminum nitrate solution.
[0117] FIG. 15 illustrates the discharge of a battery having a
glass microfiber separator with 1.0 .mu.m pores at a current
densities of 20 .mu.A/cm.sup.2 (curve 1) and 40 .mu.A/cm.sup.2
(curve 2). The battery was assembled in a 2032 coin cell format and
had an anode comprising an aluminum foil treated with LiOH as
described in Example 1, a cathode comprising acid-treated lithium
manganese oxide, and the electrolyte was an 0.5 M aqueous aluminum
nitrate solution.
[0118] In addition, as a result of lowered internal resistance,
separators with larger pore sizes enabled a higher voltage of
operation, even at significantly higher current densities. For
example, at a current density of about 20 .mu.A/cm.sup.2, a
polypropylene separator (0.067 .mu.m pore size), a nylon separator
(0.8 .mu.m pore size) and a glass microfiber separator (1 .mu.m
pore size) displayed an average discharge potential of 1.01 V, 1.17
V and 1.18 V respectively. See FIG. 12. Table 3, below, summarizes
the average charge and discharge potential and the typical charge
and discharge voltage hysteresis values for batteries constructed
with various separators, compared against baseline (standard 0.067
.mu.m pore size polypropylene separator tested at a current density
of about 10 .mu.A/cm.sup.2).
TABLE-US-00003 TABLE 3 Charge & Discharge Characteristics For
Specific Current Densities And Separators Average Discharge Average
Charge Current Discharge Hyster- Charge Hyster- Density Voltage
esis Voltage esis Separator (.mu.A/cm.sup.2) (V) (.DELTA.V) (V)
(.DELTA.V) Polypropylene 10 1.11 30 1.20 40 (0.067 .mu.m) Mixed
cellulose 20 1.11 40 1.26 50 ester (0.2 .mu.m) Nylon (0.45 .mu.m)
20 1.12 60 1.33 100 Nylon (0.8 .mu.m) 20 1.17 53 1.34 72 40 1.03 99
1.40 221 Glass Microfiber 20 1.18 47 1.38 64 (1 .mu.m) 40 1.09 72
1.39 109
[0119] Table 3 shows that batteries having nylon or glass
microfiber separators produced higher voltages (1.17 V-1.18 V)
compared to standard polypropylene separators (1.11 V) even at
twice the current density. In further studies, the discharge and
charge hysteresis voltages (voltage difference between
end-of-charge and start-of-discharge and end-of-discharge and
start-of-charge respectively) were found to be within sufficiently
acceptable values even at four-fold higher current densities (data
not shown).
[0120] Other suitable separators also include, but are not limited
to, polyvinylidene fluoride, polytetrafluoroethylene, cellulose
acetate, nitrocellulose, polysulfone, polyether sulfone,
polyacrylonitrile, polyamide, polyimide, polyethylene, and
polyvinylchloride. In addition, anion exchange membranes and proton
exchange membranes such as NAFION.RTM. may be used as the
separator. Ceramic separators including, but not limited to,
alumina, zirconia oxides and silicon oxides can also be used. As
identified through the tests, the separators can have a pore size
ranging between 0.067 .mu.m and 1.2 .mu.m. However, separators with
lower or higher porosities and thicknesses can also be used for
specific applications.
Example 5
Solid Polymer Electrolytes
[0121] As an alternative to the liquid aqueous electrolyte, a solid
polymer electrolyte (SPE) incorporating at least one aluminum salt
with or without one or more sources of hydroxides can be used in
certain embodiments. Not only does the use of SPEs allow higher
operating voltages, it enables a stable reaction dynamic over a
wide range of operating conditions (temperature, humidity,
mechanical stresses, etc.). While the aluminum salt ensures
efficient flow of aluminum ions through the electrolyte, added
hydroxides contribute OH.sup.- to enable the formation of
Al(OH).sub.4.sup.1- ions during the transportation of ions.
Aluminum salts include but are not limited to Al(NO.sub.3).sub.3,
Al.sub.2(SO.sub.4).sub.3 and AlCl.sub.3 and combinations and
variations thereof. Hydroxides include but are not limited to
Al(OH).sub.3, LiOH, NaOH, KOH, Ca(OH).sub.3, Mg(OH).sub.2 and
NH.sub.4OH and mixtures thereof. In general, the polymer is
selected from the group consisting of polytetrafluoroethylene,
acetonitrile butadiene styrene, styrene butadiene rubber, ethyl
vinyl acetate, poly(vinylidene fluoride-co-hexafluoropropylene),
polymethyl methacrylate, and mixtures thereof.
[0122] Aluminum Salt-Based SPEs: In a certain embodiment, a
cross-linking polymer such as poly(vinylidene
fluoride-co-hexafluoropropylene) (PVDF-HFP) or polymethyl
methacrylate (PMMA) is mixed with aluminum nitrate in a ratio
ranging between 1:1 and 1:10. The mixture is then dissolved in a
solvent such as N-methyl pyrrolidone or dimethyl sulfoxide and
heated at temperatures ranging from 50-200.degree. C. under
constant stirring for 2 hours in order to initiate the
polymerization reaction. The solution is observed to turn viscous,
following which it is transferred to a vacuum furnace chamber where
it is further heated at the above temperature range for 2-24 hours
in order to remove the solvent and obtain the resultant solid
polymer electrolyte. The produced solid polymer electrolyte
comprises the aluminum salt and the cross-linking polymer in the
weight ratio that was selected, typically the cross-linking polymer
at 9-50 wt % and the aluminum salt at 50-91 wt %).
[0123] In another embodiment, the cross-linking polymer may be
mixed with aluminum halides (such as AlCl.sub.3, AlBr.sub.3,
AlI.sub.3) and 1-ethyl-3-methylimidazolium chloride (EMIMC1,
Sigma-Aldrich), 1-ethyl-3-methylimidazolium bromide (EMIMBr,
Sigma-Aldrich), or 1-ethyl-3-methylimidazolium iodide (EMIMI,
Sigma-Aldrich), where the ratio of the aluminum halide to the
1-ethyl-3-methylimidazolium halide ranges from 1:1 to 5:1
(weight:weight). The combined aluminum halide and 1-ethyl
methylimidazolium halide is then mixed with the cross linking
polymer such as PVDF-HFP or PMMA in a ratio of 1:1 to 10:1
(weight:weight). Typically, 0.1 to 1 g of the mixture per mL of
solvent is combined with a solvent such as solvent can be N-methyl
pyrrolidone or DMSO. The mixing and heating steps are similar to
the process described above. The resultant solid polymer
electrolyte will contain aluminum salt, 1-ethyl methylimidazolium
halide and the cross-linking polymer in the weight ratio that was
chosen, typically the cross-linking polymer at 9-50 wt % and the
aluminum salt at 50-91 wt %.
[0124] The mixture dissolved in the solvent is heated between about
50.degree. C. and 200.degree. C. for 2-24 hours under constant
stirring. In one example, the mixture was heated at 90.degree. C.
continuously for 2 hours under constant stirring. This step
initiates the polymerization reaction. At the end of this step, the
solution turns viscous indicating successful completion of the
polymerization reaction. The mixture is then poured into a flat
glass petri dish or other suitable container and transferred to a
vacuum furnace where it is heated between 50.degree. C. and
200.degree. C. overnight or for as long as necessary to completely
remove the solvent. At the end of this step, a free-standing SPE is
obtained that can be released from the glass surface either
mechanically (peeling off) or through the application of ethanol. A
photograph of a SPE is shown in FIG. 16, which shows the
cylindrical, free-standing, translucent solid polymer electrolyte
that is about 1 mm thick and about 3 cm in diameter.
[0125] Introduction of Hydroxides in SPEs: The addition of
hydroxides to the electrolyte. described in Example 3, above, can
be achieved by introducing a suitable hydroxide in the mixture in
addition to the cross-linking polymer and aluminum salt. In one
embodiment, 100 mg lithium hydroxide and 900 mg aluminum nitrate
were added to about 5 mL deionized water which resulted in the
formation of aluminum hydroxide by the following reaction:
3LiOH+Al(NO.sub.3).sub.3.fwdarw.Al(OH).sub.3+3LiNO.sub.3 (10).
[0126] In a separate container, poly(vinylidene
fluoride-co-hexafluoropropylene) (PVDF-HFP, Sigma-Aldrich) was
dissolved in acetone, at a concentration of 500 mg of the polymer
in 5 mL acetone, through bath sonication for up to 6 hours, while
the bath itself was maintained at a temperature of 60.degree. C.
The volume of acetone was maintained at 5 mL through subsequent
addition of the solvent as and when required. Upon dissolution of
PVDF-HFP in acetone, 5 mL of the solution was added to 5 mL of the
aqueous electrolyte solution comprising the reaction products of
lithium hydroxide and aluminum nitrate dispersed in DI water. The
addition of the PVDF-HFP solution to the aqueous electrolyte
solution initiated a polymerization reaction which resulted in the
formation of a free-standing solid polymer electrolyte as shown in
the inset of FIG. 17.
[0127] In a particular embodiment, a solid polymer electrolyte
prepared by the method described in the above paragraph was tested
in a 2032 coin cell comprising of a cathode comprising manganese
oxide treated by acid-based delithiation followed by lithium
hydroxide etching of the cathode, and an anode comprising aluminum
foil treated as described in Example 1. No separators or liquid
electrolytes were used and the solid polymer electrolyte was
sandwiched between the anode and cathode.
[0128] FIG. 17 illustrates the voltage profile of a battery having
a solid-polymer electrolyte, showing a short duration of discharge
at 50 .mu.A/cm.sup.2, followed by discharging at 20 .mu.A/cm.sup.2
and charging at a current density of 20 .mu.A/cm.sup.2, with an
inset of a photograph of solid polymer electrolytes, indicated by
arrows.
Example 6
Charge and Discharge Cycles
[0129] An embodiment of a system useful for changing and
discharging the disclosed aluminum ion batteries is illustrated in
FIG. 10. In addition to standard galvanostatic (constant current)
charge cycles, potentiostatic or a combination of potentiostatic
and galvanostatic charge cycles were shown to have an impact on the
performance, specifically in terms of faster reaction kinetics
(rate capability). The range of voltages for potentiostatic charge
was identified to lie between 1.5 V and 2 V, while the optimum
value was identified to be about 1.8 V. At voltages greater than 2
V significant electrolysis was observed, confirmed by a rapid rise
in currents.
[0130] The observed increase in rate capability could be attributed
to the presence of a stronger electromotive force to aid in the
transport of aluminum-based ions from the cathode back to the
anode, which would cause few or no aluminum ions to be lost through
side reactions in the electrolyte and thereby a steady electric
field is maintained to guide the direction of flow of ions. In
addition to galvanostatic, potentiostatic and
galvanostatic-potentiostatic charge cycles, a constant voltage
sweep rate can be applied to charge the cell in certain
embodiments. In certain embodiments, the dV/dt value of the
constant voltage sweep rate is from 0.01 mV/second to 100
mV/second. Galvanostatic charge and constant voltage sweep rate
charge can both be applied in conjunction with a final constant
voltage charge to ensure completion of the charge cycle. Typically,
in certain embodiments, the final constant voltage charge is
maintained to achieve trickle charge until the current drops below
a pre-determined value ranging from 1% to 50% of the current
applied during galvanostatic charge cycle.
[0131] In certain embodiments, the discharge step can be a
combination of high and low current density galvanostatic steps,
allowing the cell chemistry to optimize coulombic efficiency and
ensure maximum diffusion of active ions and its participation in
electron-exchange reactions. Since the discharge process is a
function of the rate at which aluminum ions diffuse through
manganese oxide, such a combination of high and low current
prevents the build-up of localized charge at the
cathode-electrolyte interface and optimizes the efficiency of the
cell.
[0132] While not wishing to be bound by theory, it is believed that
as small regions at the cathode-electrolyte interface continue to
build up charge at relatively high current densities, the flow of
ions gets impeded and the reaction kinetics become slower.
Therefore, a method that follows such a high current draw with a
short period of low current density discharge enables dissipation
of this localized charge build-up, helping the ions diffuse through
the surface and into the longitudinal depths of the cathode and as
a result, freeing up the surface of the cathode for subsequent ions
to diffuse through to the bulk of cathode. It is believed that at
higher current densities, aluminum ions do not have sufficient time
to diffuse through the bulk of cathode, resulting in a localized
charge build-up at the cathode-electrolyte interface. As the high
current density is momentarily replaced by a lower current density,
aluminum ions begin diffusing through the bulk of the cathode,
resulting in a reduction in the localized charge build-up at the
cathode-electrolyte interface.
[0133] A typical voltage profile produced using such a discharge
profile incorporating a combination of low-current and high-current
pulses is shown in FIG. 18. FIG. 18 shows a discharge profile
produced by a combination of low-current and high-current pulses.
The battery was assembled in a 2032 coin cell format and had an
anode comprising an aluminum foil treated with LiOH as described in
Example 1, a cathode comprising acid-treated lithium manganese
oxide, a 0.5 M aluminum nitrate (aq) electrolyte and a 25 .mu.m
thick polypropylene separator with an average pore size of 0.067
.mu.m. The current densities were switched between 100 A/g
(low-current pulse) and 500 A/g (high-current pulse), where the
current is normalized with respect to the mass of the cathode.
Similar approaches can be used with a system such as the one
illustrated in FIG. 10 to improve the overall performance of the
battery.
[0134] While the disclosure has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the disclosure. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
disclosure without departing from the essential scope thereof.
Therefore, it is intended that the disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this disclosure, but that the disclosure will include
all embodiments falling within the scope of the appended
claims.
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