U.S. patent application number 16/049535 was filed with the patent office on 2019-01-31 for electrochemical cell with getter and method of forming same.
The applicant listed for this patent is Pellion Technologies. Invention is credited to Robert Ellis Doe, Craig Downie, David Eaglesham.
Application Number | 20190036179 16/049535 |
Document ID | / |
Family ID | 65038233 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190036179 |
Kind Code |
A1 |
Downie; Craig ; et
al. |
January 31, 2019 |
ELECTROCHEMICAL CELL WITH GETTER AND METHOD OF FORMING SAME
Abstract
An electrochemical cell including a getter material, a battery
including the electrochemical cell, and methods of forming the
electrochemical cell and battery are disclosed.
Inventors: |
Downie; Craig; (Waltham,
MA) ; Doe; Robert Ellis; (Medfield, MA) ;
Eaglesham; David; (Lexington, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pellion Technologies |
Woburn |
MA |
US |
|
|
Family ID: |
65038233 |
Appl. No.: |
16/049535 |
Filed: |
July 30, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62539393 |
Jul 31, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/13 20130101; H01M
2300/0037 20130101; H01M 4/62 20130101; H01M 10/0569 20130101; Y02E
60/10 20130101; H01M 10/0525 20130101; H01M 10/052 20130101; H01M
10/52 20130101; H01M 10/0568 20130101; H01M 2/1686 20130101; H01M
4/366 20130101; H01M 10/058 20130101; C01D 15/02 20130101; H01M
10/0567 20130101 |
International
Class: |
H01M 10/52 20060101
H01M010/52; H01M 10/0525 20060101 H01M010/0525; H01M 10/0569
20060101 H01M010/0569; H01M 10/0568 20060101 H01M010/0568; H01M
10/058 20060101 H01M010/058 |
Claims
1. An electrochemical cell comprising: a first electrode; a second
electrode; a separator between the first electrode and the second
electrode; a non-aqueous electrolyte comprising one or more salts;
and a getter material comprising one or more gas getters, wherein
the one or more gas getters are in direct contact with, form part
of, or both one or more of the first electrode, the second
electrode, the separator, and the non-aqueous electrolyte.
2. The electrochemical cell of claim 1, wherein the one or more
salts do not readily hydrolyze.
3. The electrochemical cell of claim 1, wherein the non-aqueous
electrolyte comprises a fluid.
4. The electrochemical cell of claim 1, wherein the one or more gas
getters comprise at least one of a metal oxide, a metal hydroxide,
or both the metal oxide and the metal hydroxide.
5. The electrochemical cell of claim 2, wherein the one or more
salts do not comprise an anion selected from the group consisting
of PF.sub.6.sup.-1, BF.sub.4.sup.-1, AlCl.sub.4.sup.-1,
AsF.sub.6.sup.-1, ClO.sub.4.sup.-1, SiF.sub.6.sup.-1, or
SbF.sub.6.sup.-1.
6. The electrochemical cell of claim 2 wherein the one or more
salts do not comprise any of LiPF.sub.6, LiBF.sub.4, LiAlCl.sub.4,
LiAsF.sub.6, LiClO.sub.4, LiSiF.sub.6, or LiSbF.sub.6.
7. The electrochemical cell of claim 1, wherein the non-aqueous
electrolyte comprises one or more lithium salts of at least one of
the following anions: triflate (CF.sub.3SO.sub.3.sup.-1),
triflinate (CF.sub.3SO.sub.2.sup.-1), perfluorobutanesulfonate
(C.sub.4F.sub.9SO.sub.3.sup.-1), bis(perfluoroalkylsulfonyl)imide
[N((C.sub.xF.sub.2x+1).sub.xSO.sub.2).sub.2.sup.-1],
bis(trifluoromethane)sulfonimide
[N(CF.sub.3SO.sub.2).sub.2.sup.-1],
bis(perfluoroethylsulfonyl)imide
[N(C.sub.2F.sub.5SO.sub.2).sub.2.sup.-1], bis(fluorosulfonyl)imide
[N(SO.sub.2F).sub.2.sup.-1], bis(perfluoropinacolato)borate
[B(C.sub.6F.sub.12O.sub.2).sub.2.sup.-1], bis(oxalato)borate
[B(C.sub.2O.sub.4).sub.2.sup.-1], difluoro(oxalato)borate
[BF.sub.2(C.sub.2O.sub.4).sup.-1], difluoro(malonato)borate
[BF.sub.2(C.sub.3H.sub.2O.sub.4).sup.-1], bis(benzenesulfonyl)imide
[N(C.sub.6H.sub.5SO.sub.2).sub.2.sup.-1], and bis(salicylato)borate
[B(C.sub.7H.sub.4O.sub.3).sub.2.sup.-1].
8. The electrochemical cell of claim 1, wherein the getter material
is incorporated into a coating that is applied to one or more of
the first electrode, the second electrode, and the separator.
9. The electrochemical cell of claim 1, wherein the one or more
salts comprise at least three elements and include two or more of
the following: boron, phosphorous, fluorine, carbon, nitrogen,
sulfur, and oxygen.
10. The electrochemical cell of claim 1, wherein the one or more
gas getters comprise one or more compounds selected from the group
consisting of: LiOH, Li.sub.2O, NaOH, Na.sub.2O, KOH, K.sub.2O,
Mg(OH).sub.2, MgO, Ca(OH).sub.2, and CaO, in any combination.
11. The electrochemical cell of claim 1, wherein a concentration of
the salt, or a combination of the one or more salts in the
non-aqueous electrolyte ranges from about 0.01 M to about 10 M.
12. The electrochemical cell of claim 1, wherein the getter
material comprises one or more of carbon, polymer, resin, metal, or
ceramic.
13. The electrochemical cell of claim 12, wherein the getter
material does not comprise any of a silica gel, an alumina, or a
zeolite.
14. The electrochemical cell of claim 1, wherein the
electrochemical cell is configured to charge to greater than or
equal to 4.0 V.
15. The electrochemical cell of claim 1, wherein at least one of
the first electrode and the second electrode comprises a metal, an
alloy, or an intermetallic compound configured to provide >1000
mAh/cc.
16. The electrochemical cell of claim 1, wherein at least one of
the first electrode and the second electrode comprises a material
configured to undergo an insertion reaction, an alloying, an
intercalation, a disproportionation, a conversion reaction, or any
combination thereof.
17. A battery comprising one or more electrochemical cells of claim
1.
18. A method of forming an electrochemical cell, the method
comprising the steps of: forming a structure comprising a first
electrode, a second electrode, and a separator there between;
providing a mixture of getter material and a liquid to the
structure, wherein the getter material directly contacts one or
more of the first electrode, the second electrode, and the
separator; removing at least a portion of the liquid; and after
removing at least a portion of the liquid, adding an electrolyte
solution to the structure.
19. The method of claim 18, wherein the electrolyte solution
comprises at least one of the following anions triflate
(CF.sub.3SO.sub.3.sup.-1), triflinate (CF.sub.3SO.sub.2.sup.-1),
perfluorobutanesulfonate (C.sub.4F.sub.9SO.sub.3.sup.-1),
bis(perfluoroalkylsulfonyl)imide
[N((C.sub.xF.sub.2x+1).sub.xSO.sub.2).sub.2.sup.-1],
bis(trifluoromethane)sulfonimide
[N(CF.sub.3SO.sub.2).sub.2.sup.-1],
bis(perfluoroethylsulfonyl)imide
[N(C.sub.2F.sub.5SO.sub.2).sub.2.sup.-1], bis(fluorosulfonyl)imide
[N(SO.sub.2F).sub.2.sup.-1], bis(perfluoropinacolato)borate
[B(C.sub.6F.sub.12O.sub.2).sub.2.sup.-1], bis(oxalato)borate
[B(C.sub.2O.sub.4).sub.2.sup.-1], difluoro(oxalato)borate
[BF.sub.2(C.sub.2O.sub.4).sup.-1], difluoro (malonato)borate
[BF.sub.2(C.sub.3H.sub.2O.sub.4).sup.-1], bis(benzenesulfonyl)imide
[N(C.sub.6H.sub.5SO.sub.2).sub.2.sup.-1], and bis(salicylato)borate
[B(C.sub.7H.sub.4O.sub.3).sub.2.sup.-1].
20. The method of claim 18, wherein the getter material comprises
one or more compounds selected from the group consisting of: LiOH,
Li.sub.2O, NaOH, Na.sub.2O, KOH, K.sub.2O, Mg(OH).sub.2, MgO,
Ca(OH).sub.2, and CaO.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present disclosure claims the benefit of U.S.
Provisional Patent Application No. 62/539,393, filed on Jul. 31,
2017 and entitled "ELECTROCHEMICAL CELL WITH GETTER AND METHOD OF
FORMING SAME," which is incorporated herein by reference.
FIELD OF INVENTION
[0002] The disclosure generally relates to electrochemical cells.
More particularly, exemplary embodiments of the present disclosure
relate to electrochemical cells including a getter.
BACKGROUND OF THE DISCLOSURE
[0003] Electrochemical cells, such as rechargeable or secondary
electrochemical cells, can be used to power a variety of devices,
such as mobile phones, portable computers, other portable devices,
electric or hybrid cars, as well as many other appliances. For many
applications, it is desirous to use electrochemical cells with
relatively high energy density (energy that can be derived from a
cell per unit volume of the cell), relatively high specific energy
density (energy that can be derived per unit weight of the cell or
per unit weight of the active electrode material), and/or
relatively high average discharge potential of the cell, so that
desired energy can be supplied to a device using the cell, while
minimizing the mass and/or volume of the cell.
[0004] Generally, electrochemical cells include an anode, a
cathode, a separator between the anode and cathode, and an
electrolyte. During discharge of an electrochemical cell, an
oxidation-reduction reaction occurs, causing electrons flow,
through an external circuit, from the anode to the cathode, and
cations are attracted from the anode to the cathode. In the case of
secondary electrochemical cells, the cells can be recharged by
causing electrons and cations to flow in the opposite direction
using a charger.
[0005] During discharging and/or charging of electrochemical cells,
particularly of high-energy electrochemical cells (e.g.,
electrochemical cells with an average discharge potential of 3.5
Volts or more), undesired reactions of one or more components
within an electrochemical cell (e.g., between one or more
components of the electrolyte and/or between one or more components
within an electrolyte and one or more components of an anode and/or
a cathode) can occur, resulting in undesired gas production within
the cell. For example, one or more of electrolyte components can
oxidize or otherwise degrade to form unwanted gas. The produced gas
can cause an increase in the cell volume, thereby reducing the
energy density of the cell, can cause a reduction of the capacity
of the electrochemical cell, can deleteriously affect other
discharge performance of the cell, and/or can be a safety
hazard.
[0006] Various attempts to capture gas that is produced in
electrochemical cells have been developed. For example, getter
material that is sealed apart from the electrochemical cell has
been used to capture gas, such as carbon dioxide formed within an
electrochemical cell. Unfortunately, placing a seal between the
getter material and the electrochemical cell can add undesired
weight and/or volume to the electrochemical cell and can prevent
the getter material from addressing gas production during regular
charging and discharging of the electrochemical cell.
[0007] U.S. Pat. No. 4,448,860, in the name of von Alpen et al.,
discloses a cell that is protected against the danger of corrosion
of the alkali metal electrode, particularly due to moisture
penetrating from the outside the cell, by providing the cell with a
gas-absorbing getter material. The gas-absorbing getter material is
designed to mitigate danger associated with in-flowing ambient
oxygen, CO.sub.2, or inwardly diffusing water. The reference does
not disclose techniques for addressing gasses that form as a result
of high-energy cell operation.
[0008] U.S. Pat. No. 7,776,465, in the name of Hatazawa et al.,
discloses a battery that includes an outer covering member that
includes a laminated film and battery element (electrochemical
cell) contained within the outer covering member and sealed
therein. The outer covering member includes a gas absorbable
material interposed between the outermost layer of the outer
covering member and the battery element. In other words, the
gas-absorbable material is not part of the electrochemical cell,
but rather is separated from the electrochemical cell and included
in an outer covering member.
[0009] U.S. Pat. No. 8,460,808, in the name of Toia et al.,
discloses a rechargeable battery that includes means for sorbing
harmful substances. The means includes a polymeric housing that is
permeable to said harmful substances but impermeable to the
electrolyte. One or more getter materials for the sorption of said
harmful substances are included within the polymeric housing.
[0010] U.S. Pat. No. 8,834,180, in the name of Woo et al.,
discloses a secondary battery that includes an electrode assembly,
a gas-collecting member, and a battery case. The electrode assembly
includes first and second electrode plates and a separator
interposed between the first and second electrode plates. The
gas-collecting member is provided separately and adjacent to the
electrode assembly. The battery case encases the electrode assembly
and the gas-collecting member.
[0011] U.S. Pat. No. 9,114,382, in the name of Visconti et al.,
discloses a carbon dioxide composite getter that includes an
envelope that is permeable to CO.sub.2 and powders of a first and a
second active material contained within the envelope. The first
active material is lithium hydroxide and the second active material
is lithium oxide. The getter is separate from the electrochemical
cell, and thus adds significant volume to a battery.
[0012] Each of the above-described electrochemical cells suffers
various drawbacks. Accordingly, improved electrochemical cells
including getter material, batteries including the electrochemical
cells, and methods of forming the same are desired.
SUMMARY OF THE DISCLOSURE
[0013] Various embodiments of the present disclosure provide
improved electrochemical cells including getter material, including
one or more gas getters, in direct contact with one or more
components of the electrochemical cells--i.e., the getter material
or getters are not contained in a separate envelope or container.
This allows the getter(s) to work efficiently, without adding
significant weight or volume to the cells or batteries including
the cells. Use of getters in direct contact with one or more
components of the electrochemical cell can also efficiently capture
gas that forms within the cell (e.g., within an electrolyte of the
cell) during use and/or facilitate high voltage operation of the
cells.
[0014] In accordance with at least one exemplary embodiment of the
disclosure, an electrochemical cell, such as a secondary or
rechargeable electrochemical cell, includes a first electrode, a
second electrode, a separator between the first electrode and the
second electrode, a non-aqueous electrolyte, and a getter material
comprising one or more gas getters (also referred to herein simply
as getter or getters), wherein the one or more gas getters are in
direct contact with, form part of, or both one or more of the first
electrode, the second electrode, the separator, and the non-aqueous
electrolyte. In accordance with various aspects of these
embodiments, the non-aqueous electrolyte comprises a salt that does
not readily hydrolyze. In accordance with some aspects of these
embodiments, the one or more salts do not comprise an anion
selected from the group consisting of PF.sub.6.sup.-1,
BF.sub.4.sup.-1, AlCl.sub.4.sup.-1, AsF.sub.6.sup.-1,
ClO.sub.4.sup.-1, SiF.sub.6.sup.-1, or SbF.sub.6.sup.-1. Exemplary
salts suitable for use in exemplary electrolytes comprise at least
three elements and include two or more of the following: boron,
phosphorous, fluorine, carbon, nitrogen, sulfur, and oxygen.
Non-limiting examples of exemplary salts of the disclosure include
use of one or more salts comprise one or more anions selected from
the group consisting of triflate (CF.sub.3SO.sub.3.sup.-1),
triflinate (CF.sub.3SO.sub.2.sup.-1), perfluorobutanesulfonate
(C.sub.4F.sub.9SO.sub.3.sup.-1), bis(perfluoroalkylsulfonyl)imide
[N((C.sub.xF.sub.2x+1).sub.xSO.sub.2).sub.2.sup.-1],
bis(trifluoromethane) sulfonimide
[N(CF.sub.3SO.sub.2).sub.2.sup.-1],
bis(perfluoroethylsulfonyl)imide
[N(C.sub.2F.sub.5SO.sub.2).sub.2.sup.-1], bis(fluorosulfonyl)imide
[N(SO.sub.2F).sub.2.sup.-1], bis(perfluoropinacolato)borate
[B(C.sub.6F.sub.12O.sub.2).sub.2.sup.-1], bis(oxalato)borate
[B(C.sub.2O.sub.4).sub.2.sup.-1], difluoro (oxalato) borate
[BF.sub.2(C.sub.2O.sub.4).sup.-1], difluoro(malonato) borate
[BF.sub.2(C.sub.3H.sub.2O.sub.4).sup.-1], bis(benzenesulfonyl)imide
[N(C.sub.6H.sub.5SO.sub.2).sub.2.sup.-1], and bis(salicylato)borate
[B(C.sub.7H.sub.4O.sub.3).sub.2.sup.-1]. The one or more salts
include a cation, such as lithium. In accordance with further
aspects, the electrochemical cell is a high-energy rechargeable
electrochemical cell with having an average discharge potential of
.gtoreq.3.5 V, .gtoreq.4 V, .gtoreq.4.25 V, or .gtoreq.4.5 V. In
accordance with further aspects, the electrochemical cell is a
high-energy rechargeable electrochemical cell having an upper
charge cutoff potential of .gtoreq.4.3 V, .gtoreq.4.35 V,
.gtoreq.4.4 V, or .gtoreq.4.45 V. The electrolyte can be a fluid,
such as a liquid or a gel, which may also be in contact with solid
ion conductors at least incorporated into the cell electrolyte in
part (e.g., polymer, glass, ceramic). The first electrode can
include Li, Li alloys such as Si, Sn, Bi, Al,
Li.sub.4Ti.sub.5O.sub.12, hard carbon, graphitic carbon, and
amorphous carbon. The second electrode can include second electrode
active material, such as transition metal oxides, transition metal
oxo-anions, chalcogenides, halogenides and combinations thereof.
Non-limiting examples of transition metal oxides comprised of one
or more transition metals and one or more redox active transition
metals such as Lithium Cobalt Oxide, Lithium Nickel Manganese
Cobalt Oxide, and Lithium Nickel Cobalt Aluminum Oxide
compositions. Non-limiting examples of positive electrode active
materials for the Li battery include Lithium metal phosphates and
tavorites such as LiFePO.sub.4, Lithium metal oxide spinels
LiMn.sub.2O.sub.4, and Li NASICON's
Li.sub.3V.sub.2(PO.sub.4).sub.3. The separator can include, for
example, porous polypropylene, porous polyethylene, aramid fiber,
or glass fiber. The one or more gas getters can include at least
one of a metal oxide and a metal hydroxide, such as one or more
compounds selected from the group consisting of: LiOH, Li.sub.2O,
NaOH, Na.sub.2O, KOH, K.sub.2O, Mg(OH).sub.2, MgO, Ca(OH).sub.2,
and CaO in any combination. The getter material can further include
one or more of carbon, polymer, resin, metal, or ceramic in any
combination. In accordance with exemplary aspects, the getter
material does not include any of a silica gel, an alumina, or a
zeolite. The getter material can be included as part of a coating
that is applied to one or more of the first electrode, the second
electrode, and the separator. Additionally or alternatively, the
getter material can be incorporated into one or more of the first
electrode, the second electrode, the separator, and the
electrolyte.
[0015] In accordance with further exemplary embodiments, a
composite getter includes one or more gas getters or gas getter
materials (e.g., as described herein) dispersed in a non-aqueous
fluid. The gas getter(s) and/or getter material(s) can be dispersed
in a non-aqueous fluid as a mixture, suspension, or colloid. The
non-aqueous fluid can include one or more (e.g., lithium) salts
that do not readily hydrolyze or dissolve in the one or more
non-aqueous solvents. In accordance with some aspects of these
embodiments, the one or more salts do not comprise an anion
selected from the group consisting of PF.sub.6.sup.-1,
BF.sub.4.sup.-1, AlCl.sub.4.sup.-1, AsF.sub.6.sup.-1,
ClO.sub.4.sup.-, SiF.sub.6.sup.-1, or SbF.sub.6.sup.-1. For
example, the one or more salt may not include the one or more salts
do not comprise any of LiPF.sub.6, LiBF.sub.4, LiAlCl.sub.4,
LiAsF.sub.6, LiClO.sub.4, LiSiF.sub.6, or LiSbF.sub.6. In
accordance with further aspects, the non-aqueous fluid comprises
one or more salts of at least one of the following anions: triflate
(CF.sub.3SO.sub.3.sup.-1), triflinate (CF.sub.3SO.sub.2.sup.-1),
perfluorobutanesulfonate (C.sub.4F.sub.9SO.sub.3.sup.-1),
bis(perfluoroalkylsulfonyl)imide
[N((C.sub.xF.sub.2x+1).sub.xSO.sub.2).sub.2.sup.-1],
bis(trifluoromethane) sulfonimide
[N(CF.sub.3SO.sub.2).sub.2.sup.-1],
bis(perfluoroethylsulfonyl)imide
[N(C.sub.2F.sub.5SO.sub.2).sub.2.sup.-1], bis(fluorosulfonyl)imide
[N(SO.sub.2F).sub.2.sup.-1], bis(perfluoropinacolato) borate
[B(C.sub.6F.sub.12O.sub.2).sub.2.sup.-1], bis(oxalato)borate
[B(C.sub.2O.sub.4).sub.2.sup.-1], difluoro (oxalato) borate
[BF.sub.2(C.sub.2O.sub.4).sup.-1], difluoro(malonato) borate
[BF.sub.2(C.sub.3H.sub.2O.sub.4).sup.-1], bis(benzenesulfonyl)imide
[N(C.sub.6H.sub.5SO.sub.2).sub.2.sup.-1], and bis(salicylato)borate
[B(C.sub.7H.sub.4O.sub.3).sub.2.sup.-1]. In accordance with
additional exemplary aspects, the one or more salts comprise at
least three elements and include two or more of the following:
boron, phosphorous, fluorine, carbon, nitrogen, sulfur, and oxygen.
The non-aqueous fluid can include at least one solvent that is a
non-aqueous polar aprotic solvent. In accordance with further
aspects, the non-aqueous fluid comprises at least one solvent
including: ethers, organic carbonates, tertiary amines, lactones,
ketones, glymes, nitriles, ionic liquids, aliphatic and aromatic
hydrocarbon solvents, and organic nitro solvents. By way of
examples, the non-aqueous fluid comprises at least one solvent
including THF, 2-methyl THF, dimethoxyethane, diglyme, triglyme,
tetraglyme, diethoxyethane, diethylether, proglyme, ethyl diglyme,
butyl diglyme, fluorinated ether, hydrofluoroethers, ethylene
carbonate, fluoro-ethylene carbonate, dimethyl carbonate, ethyl
methyl carbonate, diethyl carbonate, dimethylsulfoxide,
dimethylsulfite, sulfolane, ethyl methyl sulfone, acetonitrile,
hexane, toluene, fluoro-toluene, nitromethane, 1-3 dioxalane, 1-3
dioxane, 1-4 dioxane, trimethyl phosphate, tri-ethyl phosphate,
hexa-methyl-phosphoramide (HMPA),
N,N-propyl-methyl-pyrrolidinium-bis(trifluoromethylsulfonyl)imide
(P13-TFSI), N,N-propyl-methyl-pyrrolidinium-diacetamide (P13-DCA),
propyl-methyl-pyrrolidinium-bis(fluorosulfonyl)imide (P13-FSI),
ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulfonyl)imide
(PDEA-TFSI), and
1-(methoxyethyl)-1-methylpiperidinium-bis(trifluoromethylsulfonyl)imide
(MOEMPP-TFSI). A concentration of the salt, or a combination of the
one or more salts in the non-aqueous fluid ranges from, for
example, about 0.01 M to about 10 M. The composite getter can be
incorporated into one or more components of an electrochemical
device, such as the electrochemical cells, and batteries described
herein. For example, the composite getter can be or be incorporated
into a coating that is applied to one or more of electrodes,
packaging material, and the insulating separator of the
electrochemical cell. The electrochemical cell or device can be
configured to charge to, for example, greater than or equal to 4.0
V or other voltages described herein.
[0016] In accordance with further exemplary embodiments of the
disclosure, a battery includes one or more electrochemical cells as
described herein. The batteries can additionally include a casing
and/or one or more leads. Exemplary batteries can be in the form of
coin battery, a soft pack cell laminate, a cylindrical cell, or the
like.
[0017] In accordance with additional exemplary embodiments of the
disclosure, a method of forming an electrochemical cell includes
the steps of forming a structure comprising a first electrode, a
second electrode, and a separator between the first and second
electrodes, and providing a getter material in direct contact with
one or more of the first electrode, the second electrode, and the
separator, and the electrolyte. For example, the method can include
introducing a mixture, solution, colloid, or suspension of getter
material and a liquid to the structure, wherein the getter material
directly contacts one or more of the first electrode, the second
electrode, and the separator, removing at least a portion of the
liquid, and after removing at least a portion of the liquid, adding
an electrolyte solution to the structure. A battery can be formed
by adding a casing around the electrochemical cell. Non-limiting
examples of the liquid employed to introduce the getter material as
a mixture, solution, colloid, or suspension include water, alcohol,
ester, ketone, ether, lactam, amide, nitrile, methanol, ethanol,
isopropanol, carbonate, ethyl methyl carbonate, dimethyl carbonate,
tetrahydrofuran, 1, 2-dimethoxy ethane, acetone,
N-methyl-2-pyrrolidone, and acetonitrile.
[0018] Both the foregoing summary and the following detailed
description are exemplary and explanatory only and are not
restrictive of the disclosure or the claimed invention.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0019] A more complete understanding of the embodiments of the
present disclosure may be derived by referring to the detailed
description and claims when considered in connection with the
following illustrative figures.
[0020] FIG. 1 illustrates an electrochemical cell in accordance
with at least one exemplary embodiment of the disclosure.
[0021] FIG. 2 illustrates another electrochemical cell in
accordance with at least one exemplary embodiment of the
disclosure.
[0022] FIG. 3 illustrates a battery in accordance with at least one
exemplary embodiment of the disclosure.
[0023] FIG. 4 illustrates a typical voltage profile for a cell
containing a getter in intimate contact with an electrode assembly
and a non-aqueous electrolyte (darker line) as compared to the same
cell construction without the getter (lighter line).
[0024] FIG. 5 illustrates the mass loss for a set of 4.5 Ah cells
containing a getter in intimate contact with the electrode assembly
and non-aqueous electrolyte (A) as compared to the same cell
construction without the getter (B).
[0025] FIG. 6 illustrates the mass loss for 5 Ah cells containing a
getter in intimate contact with an electrode assembly and
non-aqueous electrolyte (C) as compared to the same cell
construction without the getter (D).
[0026] FIG. 7 illustrates a typical voltage profile for a cell
containing a getter coated upon an electrode surface in intimate
contact with non-aqueous electrolyte (darker line) as compared to
the same cell construction without the getter (lighter line).
[0027] It will be appreciated that elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements in the figures may be exaggerated relative to other
elements to help to improve understanding of illustrated
embodiments of the present disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0028] The description of exemplary embodiments of electrochemical
cells, batteries, and methods provided below is merely exemplary
and is intended for purposes of illustration only; the following
description is not intended to limit the scope of the disclosure or
the claims. Moreover, recitation of multiple embodiments having
stated features is not intended to exclude other embodiments having
additional features or other embodiments incorporating different
combinations of the stated features.
[0029] Additionally, in this disclosure, any ranges indicated may
include or exclude the endpoints. Any values of variables indicated
(regardless of whether they are indicated with "about" or not) may
refer to precise values or approximate values and include
equivalents, and may refer to average, median, representative,
majority, or a single value.
[0030] As set forth in more detail below, various embodiments of
the specification relate to electrochemical cells that include a
getter or getter material in direct contact with or that forms part
of one or more components of an electrochemical cell that can form
part of a battery. Exemplary electrochemical cells described herein
maintain a relatively high energy density, specific energy, and/or
can operate at relatively high energy levels (e.g., average
discharge voltages of .gtoreq.3.5 V, .gtoreq.4 V, .gtoreq.4.25 V,
or .gtoreq.4.5 V). In accordance with further aspects, the
electrochemical cell is a high-energy rechargeable electrochemical
cell having an upper charge cutoff potential of .gtoreq.4.3 V,
.gtoreq.4.35 V, .gtoreq.4.4 V, or .gtoreq.4.45 V. Further,
exemplary electrochemical cells are relatively safe, because the
getter captures an amount of gas that is produced within a battery
and therefore reduces a likelihood of battery rupture. Examples of
this disclosure can be used to form a variety of types of
electrochemical cells. For illustration purposes, specific
embodiments are described herein in the context of rechargeable, or
secondary, lithium-based electrochemical cells such as lithium-ion
electrochemical cells and rechargeable lithium metal cells, and
those that combine attributes of both. However, the disclosure is
not limited to such examples, unless otherwise noted.
[0031] Lithium-ion cells generally contain active materials that
operate on the principle of intercalation wherein Li+ ions migrate
in and out of host structures (e.g., graphitic negative electrodes
and layered transition metal oxide positive electrode materials)
without breaking and forming chemical bonds. Hence there is
relatively little structural change (e.g., .ltoreq.5% volume
expansion) within the electrode materials, and therefore the cell.
Generally, this provides a high degree of reversibility for the
electrochemical reactions in the cell, with minimal reaction
surface area; however it also limits the energy density of the
electrode, and therefore the cell. It is generally accepted that
significant improvement in energy density will employ higher
voltage materials (e.g., coated LiCoO.sub.2, High Ni "NMC"), or
migration away from pure intercalation reaction to those reactions
using the breaking and forming of chemical bonds, because the
latter reactions allow for denser storage of Li-ions than do
intercalation hosts. Among these are conversion, or displacement
reactions, alloying reactions, and metal deposition. That said,
dense storage of Li-ions coincides with relatively large structural
change and surface area exposure (e.g., .gtoreq.5% volume
expansion) within the electrode materials and therefore the cell.
That is, the migration towards higher energy cell chemistry
generally follows two paths: higher voltage and higher surface area
reactions to allow for denser storage of Li. A high degree of
repeated and uncontrolled surface area change and/or high voltage
can facilitate a greater degree of parasitic chemical reactions,
resulting in deterioration of the cell, cycle life, power density,
and margin for safe operation-thus offsetting gains in energy
density. Furthermore, such parasitic reactions can results in
formation of gaseous products due to parasitic reactions between
electrolyte components and/or between electrolyte components and
electrode surfaces. Electrochemical cells including a getter in
contact with or that forms part of one or more of the
electrochemical cell components can address these issues.
[0032] FIG. 1 illustrates an electrochemical cell 100 in accordance
with exemplary embodiments of the disclosure. Electrochemical cell
100 includes a first electrode 102, a second electrode 104, a
separator 106 interposed between first electrode 102 and second
electrode 104, a fluid electrolyte 112 in contact with first and
second electrodes 102, 104, and optionally includes one or more
layers (e.g., coatings) 114, 116, including getter material. As
described in more detail below, electrochemical cell 100 can
additionally or alternatively include getter material incorporated
into one or more of first electrode 102, second electrode 104,
separator 106, and/or electrolyte 112. Although electrochemical
cell 100 is illustrated with two layers 114, 116 including getter
material, as described in more detail below, electrochemical cells
in accordance with the disclosure can include additional getter
material layers, only one of layers 114, 116, or may not include
either of layers 114, 116. In the illustrated example,
electrochemical cell 100 also includes a first current collector
108 in electrical contact with first electrode 102 and a second
current collector 110 in contact with the second electrode.
[0033] First electrode 102 (also sometimes referred to herein as a
negative electrode or anode) comprises a negative electrode active
material that can accept cations. Non-limiting examples of negative
electrode active material for lithium-based electrochemical cells
include Li, Li alloys such as Si, Sn, Bi, and/or Al alloys,
Li.sub.4Ti.sub.5O.sub.12, hard carbon, graphitic carbon, and/or
amorphous carbon. Non-limiting examples of negative electrode
active material for other rechargeable electrochemical cells
include, Mg, Na, Ca, and alloys thereof, hard carbon, graphitic
carbon, and/or amorphous carbon. In accordance with some
embodiments of the disclosure, most (e.g., greater than 90 wt % to
all) of the anode active material can be initially included in a
discharged second electrode 104 (also sometimes referred to herein
as a positive electrode or cathode) when electrochemical cell 100
is initially made, so that the electrode active material forms part
of first electrode 102 during a first charge of electrochemical
cell 100--thus providing for a rechargeable electrochemical cell
wherein N/P ratio <4. That is, a rechargeable cell wherein the
capacity of the first electrode 102, N, and the capacity of the
second electrode 104, P, are configured such that N/P is <4. A
technique for depositing electroactive material on a portion of
first electrode 102 or first current collector 108 using this
technique is described in U.S. Patent Publication No. 2016/0172660,
in the name of Fischer et al., and similarly in U.S. Patent
Publication No. 2016/0172661, in the name of Fischer et al., the
contents of which are hereby incorporated herein by reference, to
the extent such contents do not conflict with the present
disclosure.
[0034] First electrode 102 and second electrode 104 can further
include one or more electronically conductive additives.
Non-limiting examples of electronically conductive additives
include carbon black, Super P.RTM., C-NERGY.TM. Super C65,
Ensaco.RTM. black, Ketjenblack.RTM., acetylene black, synthetic
graphite such as Timrex.RTM. SFG-6, Timrex.RTM. SFG-15, Timrex.RTM.
SFG-44, Timrex.RTM. KS-6, Timrex.RTM. KS-15, Timrex.RTM. KS-44,
natural flake graphite, carbon nanotubes, fullerenes, hard carbon,
or mesocarbon microbeads. First electrode 102 can include any
combination of the one or more electronically conductive
additives.
[0035] In accordance with some embodiments of the disclosure, first
electrode 102 and/or second electrode 104 further includes one or
more polymer binders. Non-limiting examples of polymer binders
include poly-vinylidene fluoride (PVdF), poly(vinylidene
fluoride-co-hexafluoropropene) (PVdF-HFP), Polytetrafluoroethylene
(PTFE), Kynar Flex.RTM. 2801, Kynar.RTM. Powerflex LBG, and
Kynar.RTM. HSV 900, and Teflon.RTM.. First electrode 102 and/or
second electrode 104 can include any combination of the one or more
polymer binders.
[0036] In accordance with further exemplary embodiments, first
electrode 102 is configured to provide >1000 mAh/cc.
Non-limiting exemplary techniques for forming such electrodes are
described in U.S. Patent Publication No. 2016/0172661.
[0037] First electrode 102 can optionally include getter material,
which includes one or more gas getters. The one or more gas getters
can comprise one or more compounds selected from the group
consisting of metal oxides and metal hydroxides. In these cases, a
molar ratio of the metal oxides:metal hydroxides can depend on
desired characteristics of the getters. For example, the getter
material can include more metal hydroxide(s) to increase a speed of
gas absorption or more metal oxide(s) to increase a capacity to
capture gas. Exemplary getters include compounds selected from the
group consisting of: LiOH, Li.sub.2O, NaOH, Na.sub.2O, KOH,
K.sub.2O, Mg(OH).sub.2, MgO, Ca(OH).sub.2, and CaO, which can be
combined in any combination, or be one compound from the group.
Exemplary molar ratios of metal oxide(s) to metal hydroxide(s)
range from about 0 to about 1, about 0.5 to about 0.5, or about 1
to about 0.
[0038] In addition to one or more getters, getter material can
include one or more of carbon, polymer, resin, metal, or ceramic,
in any combination. Such additional material(s) can be used to, for
example, facilitate incorporation of the getter into one or more
components of an electrochemical cell (e.g., electrode, separator,
or electrolyte) or coat getter material onto the one or more of the
components. In accordance with further exemplary embodiments of
this disclosure, getter material does not comprise any of a silica
gel, an alumina, or a zeolite. An amount of the one or more gas
getter can be a molar ratio equivalent (about more--e.g., about
two, five, or ten percent more) to the mols of gas (e.g., CO.sub.2,
CO, H.sub.2S, NO.sub.2, SO.sub.2, H.sub.2O, H.sub.2, O.sub.2,
C.sub.2H.sub.4, C.sub.3H.sub.6, C.sub.xH.sub.4*x, hydrocarbons)
expected to be produced during charging and/or discharging of
electrochemical cell 100.
[0039] Second electrode 104 (as noted above, also sometimes
referred to herein as a positive electrode or cathode) can include
intercalation material. Exemplary intercalation materials include
transition metal oxides, transition metal oxo-anions,
chalcogenides, halogenides and combinations thereof. Non-limiting
examples of positive electrode active materials for the lithium
electrochemical cells include lithium transition metal oxides
comprised of one or more transition metals and one or more redox
active transition metals such as lithium cobalt oxide, lithium
nickel manganese cobalt oxide compositions, lithium nickel cobalt
aluminum compositions, and lithium metal phosphates and tavorites
such as LiFePO4, lithium metal oxide spinels LiMn.sub.2O.sub.4, and
Li NASICON's Li.sub.3V.sub.2(PO.sub.4).sub.3. By way of examples
lithium nickel manganese cobalt oxide "NMC" can include a variety
of transition metal ratios and lithium excess. Exemplary NMC ratios
include, but are not limited to,
Li[Ni.sub.1/3Mn.sub.1/3Co.sub.1/3]O.sub.2 or so-called "111",
Li[Ni.sub.5/3Mn.sub.3/3Co.sub.2/3]O.sub.2 or so-called "532",
Li[Ni.sub.6/3Mn.sub.2/3Co.sub.2/3]O.sub.2 or so-called "622",
Li[Ni.sub.8/3Mn.sub.1/3Co.sub.1/3]O.sub.2 or so-called "811" either
with stoichiometric or excess lithium to transition metals. In
addition, second electrode 104 may comprise conversion, or
displacement, reaction materials. Non-limiting examples of
conversion, or displacement reaction materials includes sulfur,
metal nitrides, metal phosphides, metal sulfides, metal oxides,
metal fluorides, metal chlorides such as FeF.sub.3, FeF.sub.2,
NiF.sub.2, CO.sub.3O.sub.4, ZnF.sub.2, FeS.sub.2, Li.sub.2O and at
least one metal, LiF and at least one metal, In addition, second
electrode 104 may comprise an organic, or polymeric electro-active
material. Non-limiting examples include quinones such as dimethoxy
benzoquinone, poly-anthraquinone, graphene, graphene oxide. As
noted above, second electrode 104 can initially include most or all
of the active material for first electrode 102. Similar to first
electrode 102, second electrode 104 can optionally include getter
material as described herein.
[0040] In accordance with exemplary embodiments of the disclosure,
at least one of the first electrode 102 and the second electrode
104 include a metal, an alloy, or an intermetallic compound. In
accordance with additional or alternative exemplary embodiments, at
least one of the first electrode 102 and the second electrode 104
include a material configured to undergo an insertion reaction, an
alloying, an intercalation, a disproportionation, a conversion
reaction, or any combination thereof.
[0041] Separator 106 electrically isolates the first electrode from
the second electrode and is permeable to at least one mobile
species which is redox-active at least one of the first electrode
and the second electrode. Exemplary materials suitable for
separator 106 in accordance with embodiments of the disclosure
include porous virgin or coated polyolefin, polypropylene,
polyethylene, aramix fiber, and glass fiber. Separator 106 can
optionally comprise the getter material in part or entirely as
described herein.
[0042] Electrolyte 112 can be a fluid, e.g., a liquid or a gel
electrolyte, which may also be in contact with solid ion conductors
at least incorporated into the cell electrolyte in part (e.g.,
polymer, glass, ceramic). Electrolyte 112 generally includes a
solvent and one or more salts. Electrolyte 112 can, in some cases,
also include getter material as described herein.
[0043] A variety of non-aqueous (e.g., organic) solvents are
suitable for use in the electrolyte 112. Non-aqueous solvents can
be used alone or in any suitable combination. Whether a solvent
comprises a single non-aqueous composition or a plurality of
non-aqueous compositions, for the purposes of further exposition,
the non-aqueous solvent will be referred to as "the solvent" in the
singular. In order to provide for the reversible dissolution and
plating of an electroactive metal, the solvent advantageously
should provide appreciable solubility by coordination of the
constituent inorganic salts of the electroactive metal. In
accordance various examples, suitable solvents include non-aqueous
polar aprotic solvents, ethers, organic carbonates, and tertiary
amines, and may also include, lactones, ketones, glymes, nitriles,
ionic liquids, aliphatic and aromatic hydrocarbon solvents and
organic nitro solvents. More specifically, suitable solvents
include THF, 2-methyl THF, dimethoxyethane, diglyme, triglyme,
tetraglyme, diethoxyethane, diethylether, proglyme, ethyl diglyme,
butyl diglyme, fluorinated ether, hydrofluoroethers, ethylene
carbonate, fluoro-ethylene carbonate, dimethyl carbonate, ethyl
methyl carbonate, diethyl carbonate, dimethylsulfoxide,
dimethylsulfite, sulfolane, ethyl methyl sulfone, acetonitrile,
hexane, toluene, fluoro-toluene, nitromethane, 1-3 dioxalane, 1-3
dioxane, 1-4 dioxane, trimethyl phosphate, tri-ethyl phosphate,
hexa-methyl-phosphoramide (HMPA),
N,N-propyl-methyl-pyrrolidinium-bis(trifluoromethylsulfonyl)imide
(P13-TFSI), N,N-propyl-methyl-pyrrolidinium-diacetamide (P13-DCA),
propyl-methyl-pyrrolidinium-bis(fluorosulfonyl)imide (P13-FSI),
ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulfonyl)imide
(PDEA-TFSI), and
1-(methoxyethyl)-1-methylpiperidinium-bis(trifluoromethylsulfonyl)imide
(MOEMPP-TFSI).
[0044] Exemplary salts for electrolyte 112 do not readily
hydrolyze. For purposes of this disclosure, salts that do not
readily hydrolyze are salts that do not react with trace amounts
(e.g., <3000 ppm) water in a autocatalytic decomposition
reaction to form significant amounts (e.g., more than 300 ppm) of
strong acid such as HF or HCl. In accordance with further exemplary
embodiments, the one or more salts do not comprise an anion
selected from the group consisting of PF.sub.6.sup.-1,
BF.sub.4.sup.-1, AlCl.sub.4.sup.-1, AsF.sub.6.sup.-1,
ClO.sub.4.sup.-1, SiF.sub.6.sup.-1, or SbF.sub.6.sup.-1. Salts
including such anions are thought to be susceptible to hydrolysis.
By way of specific examples, the one or more salts do not include
any of LiPF.sub.6, LiBF.sub.4, LiAlCl.sub.4, LiAsF.sub.6,
LiClO.sub.4, LiSiF.sub.6, or LiSbF.sub.6. Exemplary compounds
suitable for the one or more salts comprise at least three elements
and include two or more of the following: boron, phosphorous,
fluorine, carbon, nitrogen, and oxygen. Non-limiting examples of
exemplary salts of the disclosure include use of one or more salts
comprise one or more anions selected from the group consisting of
triflate (CF.sub.3SO.sub.3.sup.-1), triflinate
(CF.sub.3SO.sub.2.sup.-1), perfluorobutanesulfonate
(C.sub.4F.sub.9SO.sub.3.sup.-1), bis(perfluoroalkylsulfonyl)imide
[N((C.sub.xF.sub.2x+1).sub.xSO.sub.2).sub.2.sup.-1],
bis(trifluoromethane)sulfonimide
[N(CF.sub.3SO.sub.2).sub.2.sup.-1],
bis(perfluoroethylsulfonyl)imide
[N(C.sub.2F.sub.5SO.sub.2).sub.2.sup.-1], bis(fluorosulfonyl)imide
[N(SO.sub.2F).sub.2.sup.-1], bis(perfluoropinacolato) borate
[B(C.sub.6F.sub.12O.sub.2).sub.2.sup.-1], bis(oxalato)borate
[B(C.sub.2O.sub.4).sub.2.sup.-1], difluoro (oxalato) borate
[BF.sub.2(C.sub.2O.sub.4).sup.-1], difluoro(malonato) borate
[BF.sub.2(C.sub.3H.sub.2O.sub.4).sup.-1], bis(benzenesulfonyl)imide
[N(C.sub.6H.sub.5SO.sub.2).sub.2.sup.-1], and bis(salicylato)borate
[B(C.sub.7H.sub.4O.sub.3).sub.2.sup.-1]. The cation can be lithium,
sodium, magnesium, or calcium. A concentration of the salt, or a
combination of salts in the electrolyte solution ranges from about
0.01 M to about 10 M, about 0.1 M to about 7 M, or about 0.25 to
about 7 M, or from about 0.5 M to saturation. Without wishing to be
bound by theory, it is thought that the use of non-aqueous fluid
electrolyte comprising salts that do not readily hydrolyze permits
the function of the gas getter material(s), and may in fact even
expedite the gettering activity of such materials, while in
intimate contact with the non-aqueous fluid electrolyte.
[0045] First current collector 108 and/or second current collector
110 can include any material capable of sufficiently conducting
electrons. Exemplary first/second electrode current collector
108/110 materials include aluminum, aluminum alloys, copper, copper
alloys, nickel, nickel alloys, titanium, titanium alloys, steel,
carbonaceous materials, and a metal substrate coated with an
over-layer to prevent corrosion in the electrolyte.
[0046] As noted above, electrochemical cell 100 can include one or
more layers 114, 116 of getter material. Layers 114 and/or 116 can
be initially coated onto one or more surfaces of one or more of
first electrode 102, second electrode 104 and/or separator 106.
Generally, when electrochemical cell 100 includes layer 114 and/or
layer 116, the layer(s) will be between an electrode 102 or 104
(first or second) and separator 106.
[0047] FIG. 2 illustrates another electrochemical cell 200 in
accordance with additional embodiments of the disclosure.
Electrochemical cell 200 is similar to electrochemical cell 100,
except electrochemical cell 200 includes a gate electrode 207, in
addition to the other cell components. When an electrochemical cell
includes a gate electrode, a circuit can be configured to measure
an operating parameter of the device and to determine when a cell
health event occurs and/or respond to the cell health event, as
disclosed in U.S. Patent Publication No. 2016/0006081 in the name
of Eaglesham et al., the contents of which are incorporated herein
by reference, to the extent such contents do not conflict with the
present disclosure.
[0048] In the illustrated example, electrochemical cell 200
includes a first electrode (e.g., a negative electrode) 202, a
second electrode (e.g., a positive electrode) 204, a first
separator 205, a second separator 206, a gate electrode 207 between
first electrode 202 and second electrode 204 and between first
separator 205 and second separator 206, an electrolyte 212, and
optionally includes one or more layers (e.g., coatings) 214, 216
including getter material. Electrochemical cell 200 can optionally
include getter material incorporated into one or more of first
electrode 202, second electrode 204, first separator 205, second
separator 206 and/or electrolyte 212.
[0049] First electrode 202, second electrode 204, first separator
205, second separator 206, electrolyte 212, and one or more layers
214, 216 can be the same or similar to the respective components
discussed above in connection with FIG. 1.
[0050] Gate electrode 207 is in electrochemical communication with
electrolyte 212 and permeable to at least one mobile species that
is redox-active to at least one of first electrode 202 and second
electrode 204. In the illustrated example, at least one gate
electrode 207 is situated between the first electrode 202 and
second electrode 204. By way of examples, gate electrode 207 can
include a selected one of an electronically conducting material as
freestanding form and an electronically conductive film deposited
upon an insulating substrate having porosity and tortuosity. Gate
electrode 207 can be connected to external circuit through a
dedicated tab. Other electrochemical cells with gate electrode 207
are disclosed in U.S. Patent Publication No. 2016/0006081 in the
name of Eaglesham et al.
[0051] Batteries
[0052] A battery can include one or more electrochemical cells,
such as electrochemical cell 100 or electrochemical cell 200. The
battery can be a button or coin cell battery comprising discs of
electrochemical cell components (electrode and separator) that sit
in a can base onto which a can lid is crimped. In other
embodiments, the battery is a stacked cell battery. In other
embodiments, the battery is a prismatic or pouch cell comprising
one or more stacked electrochemical cells sandwiched between
current collectors.
[0053] FIG. 3 illustrates an exemplary soft pack cell laminate
battery 300 that includes an electrochemical cell 302, which can be
the same or similar to electrochemical cell 100 or electrochemical
cell 200, and first and second tabs 306 and 308. First tab 306 can
form contact to a first electrode (e.g., first electrode 102/202);
second tab can form contact to a second electrode (e.g., second
electrode 104/204). Battery 300 can optionally include one or more
third tabs 310 that are electrically coupled to a gate electrode,
if present. Electrochemical cell 302 can include a folded
electrochemical cell (e.g., cell 100/200), which can be within a
(e.g., polymer coated aluminum foil) pouch 304. Pouch 304 can be
vacuum and heat dried, filled with electrolyte (e.g., electrolyte
112, 212), and vacuum and heat sealed. In other embodiments, the
battery is a prismatic or pouch bi-cell comprising one or more
stacks of a positive electrode that is coated with active material
on both sides and wrapped in porous separator, and a negative
electrode folded around the positive electrode, wherein one or both
current collectors can comprise carbonaceous materials. These
electrochemical cells can be folded within a (e.g., polymer coated
aluminum foil) pouch, dried under heat and/or vacuum, filled with
electrolyte, and vacuum and heat sealed. Getter material can be
added to the battery as described below. In accordance with some
embodiments, the prismatic or pouch cells include an additional tab
composed of a metal foil or carbonaceous material of the same kind
as current collectors described herein. Tab 306, 308 and/or
additional tab 310 can be affixed to the current collector by laser
or ultrasonic welding, adhesive, or mechanical contact, in order to
connect the electrodes to the device outside the packaging.
[0054] In accordance with yet additional embodiments, the battery
is a wound or cylindrical cell comprising one or more
electrochemical cells as described herein. In this case, the
battery can include wound layers of one or more stacks of a
positive electrode which comprises active material coated upon an
electronically conducting substrate, sandwiched between layers of
porous separator, and a negative electrode comprising active
material coated upon an electronically conducting substrate. The
stack(s) can be wound into cylindrical roll, inserted into the can,
dried under heat and/or vacuum, filled with electrolyte, and vacuum
and welded shut. Getter material can be added to the battery as
described below. In some embodiments of the cylindrical cells
described herein, an additional tab composed of a metal foil or
conducting material of the same kind as current collectors
described herein, is affixed to the current collector by laser or
ultrasonic welding, adhesive, or mechanical contact, in order to
connect the electrodes to an external circuit outside the
packaging.
[0055] In accordance with additional embodiments of the disclosure,
a method of forming an electrochemical cell includes forming a
structure comprising a first electrode, a second electrode, and a
separator there between, wherein the electrochemical structure
includes one or more getters as described herein. As noted above,
one or more components (e.g., first electrode, second electrode,
separator and/or electrolyte) can include getter material and/or
getter material can be coated on or layered over one or more of the
electrochemical cell components.
[0056] In accordance with some embodiments of the disclosure, a
method of forming an electrochemical cell includes providing a
mixture of getter material and a liquid (e.g., water, alcohol,
ester, ketone, ether, lactam, amide, nitrile, methanol, ethanol,
isopropanol, carbonate, ethyl methyl carbonate, dimethyl carbonate,
tetrahydrofuran, 1, 2-dimethoxy ethane, acetone,
N-methyl-2-pyrrolidone, and acetonitrile) employed to introduce the
getter material as a mixture, solution, or suspension to the
structure, wherein the getter material directly contacts one or
more of the first electrode, the second electrode, and the
separator, removing at least a portion of the liquid, and after
removing at least a portion of the liquid, adding an electrolyte
solution to the structure. A battery can be formed by forming
and/or sealing a casing around the electrochemical cell.
EXAMPLES
[0057] The following non-limiting examples illustrate comparative
electrochemical cells and electrochemical cells in accordance with
exemplary embodiments of the disclosure. These examples are merely
illustrative, and it is not intended that the invention be limited
to the examples.
[0058] In the following examples and the comparative example,
lithium-ion electrochemical cells were prepared by the following
steps:
Example 1
[0059] Electrochemical cells comprising a lithium cobalt oxide
"LCO" positive electrode, a polyolefin separator, and a negative
electrode of lithium metal electrochemically plated upon a copper
substrate were constructed by winding the three components in a
manner to form a flat wound, prismatic stack with a nominal
capacity of about 5.0 Ah. Subsequently the stack was sealed a
soft-pouch laminate material after being charged with an
electrolyte comprising at least in part ethylene carbonate,
dimethyl carbonate, and lithium difluoro(oxalato)borate, a salt
that does not readily hydrolyze. One cell includes a getter
comprising a mixture of Li.sub.2O and LiOH deposited in intimate
contact with the electrode assembly and electrolyte. FIG. 4
illustrates a typical voltage profile for a cell containing a
getter in intimate contact with an electrode assembly and a
non-aqueous electrolyte (darker line) as compared to the same cell
construction without the getter (lighter line). The cells depicted
are first charged at a rate of 0.2 C to greater than 4.25 V, then
discharged at a rate of 0.2 C. Subsequently they are re-charged at
a higher rate of 0.33 C to greater than 4.25 V. It is apparent by
way of comparing the shape of the voltage profile and corresponding
capacity that there is no additional electrochemical activity due
to the presence of the getter in intimate contact with the
electrode assembly and electrolyte.
Example 2
[0060] A series of cells were constructed in similar fashion as
described in Example 1 presented herein. The cells, some comprising
getter and some excluding getter, are charged to greater than 4.25
V and 4.5 Ah, then subjected to ambient humidity and a temperature
of nearly 80.degree. C. for greater than 50 hours. FIG. 5
illustrates the mass loss associated with gas evolution, and
leakage from cells. Data for "A" in FIG. 5 depicts negligible mass
loss and corresponds to cells comprising a getter in intimate
contact with the electrode assembly and non-aqueous electrolyte.
Data for "B" in FIG. 5 is for the same cell construction without
the getter, and depicts seven times higher mass loss under the same
thermal conditions.
Example 3
[0061] A series of cells were constructed in similar fashion, but
with a lithium nickel manganese oxide cathode as described in
Example 1 presented herein. The cells, some comprising getter and
some excluding getter, are charged to greater than 4.25 V and 5.0
Ah, then subjected to ambient humidity and a temperature of nearly
80.degree. C. for different periods of time. FIG. 6 illustrates the
mass loss associated with gas evolution, and leakage from cells.
Data for "C" in FIG. 6 depicts negligible mass loss after 60 hours
at temperature of nearly 80.degree. C. and corresponds to cells
comprising a getter comprising a 3:1 mixture of LiOH and Li.sub.2O
in intimate contact with the electrode assembly and non-aqueous
electrolyte. Data for "D" in FIG. 6 is for the same cell
construction without the getter, and depicts a few percent mass
loss due to a high rate of gas evolution and leakage after only 18
hours at temperature of nearly 80.degree. C.
Example 4
[0062] A positive electrode was prepared by coating a formulation
of lithium cobalt oxide, carbon, and polymeric binder from solution
of N-methyl pyrrolidinone upon an aluminum substrate. Subsequently
a composite getter comprising LiOH and carbon was spray coated upon
the positive electrode from a solution of methanol. The methanol is
subsequently removed. Electrochemical cells comprising a positive
electrode coated with LiOH and carbon composite getter, a
polyolefin separator, and a negative electrode of lithium metal
electrochemically plated upon a copper substrate were constructed
by stacking. Subsequently the stack was sealed a soft-pouch
laminate material after being charged with an electrolyte
comprising at least one non-aqueous solvent and salt that does not
readily hydrolyze. FIG. 7 illustrates a typical voltage profile for
a cell comprising a getter in intimate contact with an electrode
assembly (i.e., coated upon the positive electrode and therefore
situated in the stack between the positive electrode and separator)
and a non-aqueous electrolyte (darker line) as compared to the same
positive electrode without the getter coating in the cell
construction (lighter line). The cells depicted are charged at a
rate of 1C to greater than 4.25 V, then discharged at a rate of 1C
in this cycling scheme. It is apparent by way of comparing the
shape of the voltage profile and corresponding capacity that there
is no deleterious electrochemical activity due to the presence of
the getter in intimate contact with the electrode assembly and
electrolyte.
[0063] Although exemplary embodiments of the present disclosure are
set forth herein, it should be appreciated that the disclosure is
not so limited. For example, although the systems and methods are
described in connection with various specific chemistries, the
disclosure is not necessarily limited to these chemistries. Various
modifications, variations, and enhancements of the systems and
methods set forth herein can be made without departing from the
spirit and scope of the present disclosure.
* * * * *