U.S. patent application number 10/085303 was filed with the patent office on 2003-08-28 for non-aqueous electrochemical cell.
Invention is credited to Bowden, William L., Issaev, Nikolai N., Pozin, Michael.
Application Number | 20030162099 10/085303 |
Document ID | / |
Family ID | 27753599 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030162099 |
Kind Code |
A1 |
Bowden, William L. ; et
al. |
August 28, 2003 |
Non-aqueous electrochemical cell
Abstract
A lithium electrochemical cell includes an electrolyte having a
mixture of solvents including propylene carbonate (PC) and
dimethoxyethane (DME), and a salt mixture. The salt mixture
includes lithium trifluoromethanesulfonate (LiTFS), and lithium
trifluoromethanesulfonimid- e (LiTFSI), and the cell contains less
than 1500 ppm by weight of sodium. The mixture of solvents can
further include ethylene carbonate (EC).
Inventors: |
Bowden, William L.; (Nashua,
NH) ; Issaev, Nikolai N.; (Woodbridge, CT) ;
Pozin, Michael; (Brookfield, CT) |
Correspondence
Address: |
FISH & RICHARDSON PC
225 FRANKLIN ST
BOSTON
MA
02110
US
|
Family ID: |
27753599 |
Appl. No.: |
10/085303 |
Filed: |
February 28, 2002 |
Current U.S.
Class: |
429/333 ;
429/331 |
Current CPC
Class: |
H01M 10/0569 20130101;
H01M 6/166 20130101; H01M 10/0568 20130101; H01M 10/052 20130101;
Y10T 29/49108 20150115; H01M 6/164 20130101; Y02P 70/50 20151101;
Y02E 60/10 20130101; H01M 2300/0037 20130101 |
Class at
Publication: |
429/333 ;
429/331 |
International
Class: |
H01M 010/40 |
Claims
What is claimed is:
1. A lithium electrochemical cell, comprising: an electrolyte
comprising: a mixture of solvents comprising: propylene carbonate;
dimethoxyethane; and a salt mixture comprising: lithium
trifluoromethanesulfonate; and lithium trifluoromethanesulfonimide,
wherein the cell contains less than 1500 ppm by weight of
sodium.
2. The cell of claim 1, wherein the cell contains less than 1200
ppm by weight of sodium.
3. The cell of claim 1, wherein the cell contains less than 1000
ppm by weight of sodium.
4. The cell of claim 1, wherein the cell contains less than 800 ppm
by weight of sodium.
5. The cell of claim 1, wherein the cell contains less than 600 ppm
by weight of sodium.
6. The cell of claim 1, wherein the mixture of solvents comprises:
40-80% by weight of dimethoxyethane; and 20-60% by weight of
propylene carbonate; and the salt mixture has a concentration
between 0.4 M and 1.2 M in the mixture of solvents.
7. The cell of claim 6, wherein the mixture of solvents comprises:
50-75% by weight of dimethoxyethane; and 25-50% by weight of
propylene carbonate.
8. A lithium electrochemical cell, comprising: an electrolyte
comprising: a mixture of solvents comprising: ethylene carbonate;
propylene carbonate; and dimethoxyethane; and a salt mixture
comprising: lithium trifluoromethanesulfonate; and lithium
trifluoromethanesulfonimide, wherein the cell contains less than
1500 ppm by weight of sodium.
9. The cell of claim 8, wherein the cell contains less than 1200
ppm by weight of sodium.
10. The cell of claim 8, wherein the cell contains less than 1000
ppm by weight of sodium.
11. The cell of claim 8, wherein the cell contains less than 800
ppm by weight of sodium.
12. The cell of claim 8, wherein the cell contains less than 600
ppm by weight of sodium.
13. The cell of claim 8, wherein the mixture of solvents comprises:
less than 30% by weight of ethylene carbonate; 40-85% by weight of
dimethoxyethane; and the salt mixture has a concentration between
0.4 M and 1.2 M in the mixture of solvents.
14. The cell of claim 13, wherein the mixture of solvents
comprises: 10-20% by weight of ethylene carbonate; 50-70% by weight
of dimethoxyethane.
15. The cell of claim 14, comprising less than 500 ppm by weight of
sodium.
16. The cell of claim 13, wherein the mixture of solvents
comprises: 5-15% by weight of ethylene carbonate; 70-80% by weight
of dimethoxyethane; and 10-20% by weight of propylene
carbonate.
17. The cell of claim 16, comprising less than 500 ppm by weight of
sodium.
Description
TECHNICAL FIELD
[0001] The invention relates to non-aqueous electrochemical
cells.
BACKGROUND
[0002] Batteries are commonly used electrical energy sources. A
battery contains a negative electrode, typically called the anode,
and a positive electrode, typically called the cathode. The anode
contains an active material that can be oxidized; the cathode
contains or consumes an active material that can be reduced. The
anode active material is capable of reducing the cathode active
material.
[0003] When a battery is used as an electrical energy source in a
device, electrical contact is made to the anode and the cathode,
allowing electrons to flow through the device and permitting the
respective oxidation and reduction reactions to occur to provide
electrical power. An electrolyte in contact with the anode and the
cathode contains ions that flow through the separator between the
electrodes to maintain charge balance throughout the battery during
discharge.
[0004] It is desirable for batteries to have good capacity, after
they are produced and/or after they have been stored for extended
periods of time.
SUMMARY
[0005] The invention relates to non-aqueous electrochemical
cells.
[0006] In one aspect, the invention features a lithium
electrochemical cell including an electrolyte having a mixture of
solvents including propylene carbonate and dimethoxyethane, and a
salt mixture including lithium trifluoromethanesulfonate and
lithium trifluoromethanesulfonimide- . The cell contains less than
1500 ppm by weight of sodium.
[0007] Embodiments of the invention may include one or more of the
following features. The cell contains less than 1200 ppm, e.g.,
less than 1000 ppm, less than 800 ppm, or less than 600 ppm, by
weight of sodium. The cell includes a mixture of solvents having
40-80%, e.g., 50-75%, by weight of dimethoxyethane, and 20-60%,
e.g., 25-50%, by weight of propylene carbonate; and the salt
mixture has a concentration between 0.4 M and 1.2 M in the mixture
of solvents.
[0008] In another aspect, the invention features a lithium
electrochemical cell including an electrolyte having a mixture of
solvents including ethylene carbonate, propylene carbonate, and
dimethoxyethane, and a salt mixture having lithium
trifluoromethanesulfonate and lithium trifluoromethanesulfonimide.
The cell contains less than 1500 ppm, e.g., less than 1200 ppm,
less than 1000 ppm, less than 800 ppm, or less than 600 ppm by
weight of sodium.
[0009] Embodiments of the invention may include one or more of the
following features. The cell includes a mixture of solvents having
less than 30%, e.g. 10-20%, by weight of ethylene carbonate,
40-85%, e.g., 50-70%, by weight of dimethoxyethane; and the salt
mixture has a concentration between 0.4 M and 1.2 M in the mixture
of solvents. The cell includes a mixture of solvents including
5-15% by weight of ethylene carbonate, 70-80% by weight of
dimethoxyethane, and 10-20% by weight of propylene carbonate. The
cell contains less than 500 ppm by weight of sodium.
[0010] In another aspect, the invention features an electrolyte for
a lithium electrochemical cell consisting essentially of a mixture
of solvents including propylene carbonate and dimethoxyethane, and
a salt mixture having lithium trifluoromethanesulfonate and lithium
trifluoromethanesulfonimide. The electrolyte can be used in a cell,
e.g., one that contains less than 1500 ppm, e.g., less than 1000
ppm, or less than 500 ppm, by weight of sodium.
[0011] The electrolyte mixture can include a mixture of solvents
including 40-80%, e.g., 5075%, by weight of dimethoxyethane, and
20-60%, e.g., 25-50%, by weight of propylene carbonate; and the
salt mixture can have a concentration between 0.4 M and 1.2 M in
the mixture of solvents.
[0012] In another aspect, the invention features an electrolyte for
a lithium electrochemical cell consisting essentially of a mixture
of solvents including ethylene carbonate, propylene carbonate, and
dimethoxyethane, and a salt mixture having lithium
trifluoromethanesulfonate and lithium trifluoromethanesulfonimide.
The electrolyte can be used in a cell, e.g., one that contains less
than 1500 ppm, e.g., less than 1000 ppm, or less than 500 ppm by
weight of sodium.
[0013] The electrolyte may include a mixture of solvents including
less than 30%, e.g., 1020%, by weight of ethylene carbonate, and
40-85%, e.g., 50-70%, by weight of dimethoxyethane; and the salt
mixture may have a concentration between 0.4 M and 1.2 M in the
mixture of solvents.
[0014] The electrolyte may include a mixture of solvents including
5-15% by weight of ethylene carbonate, 70-80% by weight of
dimethoxyethane, and 10-20% by weight of propylene carbonate.
[0015] Embodiments may have one or more of the following
advantages. The cells can have good capacity, after production
and/or after storage for extended periods of time.
[0016] Other features and advantages of the invention will be
apparent from the description of the preferred embodiments thereof
and from the claims.
DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a sectional view of a nonaqueous electrochemical
cell.
DETAILED DESCRIPTION
[0018] Referring to FIG. 1, an electrochemical cell 10 includes an
anode 12 in electrical contact with a negative current collector
14, a cathode 16 in electrical contact with a positive current
collector 18, a separator 20, and an electrolyte. Anode 12, cathode
16, separator 20, and the electrolyte are contained within a case
22. The electrolytic solution includes a mixture of solvents and a
salt that is at least partially dissolved in the mixture of
solvents.
[0019] The electrolyte can be in liquid, solid or gel (polymer)
form. The electrolyte can contain an organic solvent such as
propylene carbonate (PC), ethylene carbonate (EC), dimethoxyethane
(DME), dioxolane (DO), tetrahydrofuran (THF), acetonitrile
(CH.sub.3CN), gamma-butyrolactone, diethyl carbonate (DEC),
dimethyl carbonate (DMC), ethyl methyl carbonate (EMC)
dimethylsulfoxide (DMSO), methyl acetate (MA), methyl formiate
(MF), sulfolane or combinations thereof. The electrolyte can
alternatively contain an inorganic solvent such as SO.sub.2 or
SOCl.sub.2. The solvents can be selected to provide a mixture
having a combination of physical and chemical properties. For
example, the electrolyte can include a first solvent, such as PC or
EC, that is polar, sluggishly reactive, and/or high boiling; and a
second solvent, such as DME, THF, or DMC, that is relatively less
polar, volatile, relatively non-viscous, and/or unreactive.
[0020] The electrolyte can also contain a lithium salt such as
lithium trifluoromethanesulfonate (LiTFS) or lithium
trifluoromethanesulfonimide (LiTFSI), or a combination thereof.
Additional lithium salts that can be included are listed in U.S.
Pat. No. 5,595,841, which is hereby incorporated by reference in
its entirety.
[0021] In some embodiments, cell 10 includes an electrolyte formed
of a mixture of solvents having DME and PC, and a salt mixture of
LiTFS and LiTFSI. Cell 10 can further have a low sodium
concentration. The concentration of DME in the mixture of solvents
can range from about 30% to about 85%. The concentration of DME in
the mixture of solvents can be equal to or greater than 30%, 35%,
40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%; and/or equal to or
less than 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, or 35%.
The concentration of PC in the mixture of solvents can be equal to
100% minus the concentration of DME. For example, if the
concentration of DME in the mixture of solvents is 75%, then the
concentration of PC in the mixture of solvents is 25%. If the
concentration of DME in the mixture of solvents is 50%-75%, then
the concentration of PC in the mixture of solvents is 25%-50%.
[0022] For the LiTFS and LiTFSI salt mixture, the total
concentration of salt in the mixture of solvents can range from
about 0.4 M to about 1.2 M. The total concentration of LiTFS and
LiTFSI in the mixture of solvents can be equal to or greater than
0.40 M, 0.45 M, 0.50 M, 0.55 M, 0.60 M, 0.65 M, 0.70 M, 0.75 M,
0.80 M, 0.85 M, 0.90 M, 0.95 M, 1.00 M, 1.05 M, 1.10 M, or 1.15 M;
and/or equal to or less than 1.2 M, 1.15 M, 1.10 M, 1.05 M, 1.00 M,
0.95 M, 0.90 M, 0.85 M, 0.80 M, 0.75 M, 0.70 M, 0.65 M, 0.60 M,
0.55 M, 0.50 M, or 0.45 M. Of the total concentration of salt, the
concentration of LiTFS in the mixture of solvents can be equal to
or greater than 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%,
55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%; and/or equal to or
less than 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%,
40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%. The concentration of
LiTFSI in the mixture of solvents can be equal to 100% minus the
concentration of LiTFS in the mixture of solvents. For example, if
the total concentration of salt in the mixture of solvents is 0.5
M, and the LiTFS concentration in the mixture of solvents is 90%
(i.e., 0.45 M), then the LiTFSI concentration in the electrolyte
mixture is 10% (i.e., 0.05 M). In embodiments, other types of salts
can be added to the electrolyte.
[0023] The sodium concentration described herein applies to
contents inside cell 10 plus any sodium on the inner side of case
20 and/or cap 24. For example, the sodium content may apply to the
electrolyte and a "jelly roll" inside cell 10. The jelly roll is
formed of anode 12, cathode 16, current collectors 14 and 18,
separator 20, and any protective tapes used in cell 10.
[0024] The sodium concentration in cell 10 can be between about 100
ppm to 1500 ppm by weight. The sodium concentration can be equal to
or greater than 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000,
1100, 1200, 1300, or 1400 ppm by weight; and/or equal to or less
than 1500, 1400, 1300, 1200, 1100, 1000, 900, 800, 700, 600, 500,
400, 300, 200, or 100 ppm by weight. Generally, the concentration
of sodium in cell 10 can be controlled, e.g., minimized or reduced,
by controlling the manufacturing of the cell. For example, in
embodiments in which electrolytic manganese dioxide (EMD) is used
in cathode 16, the EMD can be washed and/or neutralized after
electrodeposition with an agent that does not contain sodium or
have reduced amounts of sodium, such as LiOH. Case 20 can be
cleaned with a solution that does not contain sodium or carefully
washed. Generally, other components of cell 10, such as anode 12
and separator 20, can be similarly specified not to contain sodium
or to contain reduced amounts of sodium.
[0025] Other materials can be added to the electrolyte mixture. For
example, in certain embodiments, cell 10 includes an electrolyte
formed of a mixture of solvents including EC, DME and PC, and a
salt mixture of LiTFS and LiTFSI. The concentration of EC in the
mixture of solvents can be between about 5% and 30%. The
concentration of EC in the mixture of solvents can be equal to or
greater than 5%, 10%, 15%, 20%, or 25%; and/or equal to or less
than 30%, 25%, 20%, 15%, or 10%. The concentration of DME in the
mixture of solvents can range from about 30% to about 85%. The
concentration of DME in the mixture of solvents can be equal to or
greater than 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or
80%; and/or equal to or less than 85%, 80%, 75%, 70%, 65%, 60%,
55%, 50%, 45%, 40%, or 35%. The concentration of PC in the mixture
of solvents can be equal to 100% minus the concentration of EC and
DME. For example, if the concentration of EC in the mixture of
solvents is 15%, and the concentration of DME in the mixture of
solvents is 60%, then the concentration of PC in the mixture of
solvents is 25%. Examples of anEC:DME:PC solvent mixture are
14:62:24 and 10:75:15 by weight.
[0026] The LiTFS and LiTFSI concentrations in the electrolyte,
e.g., 0.4-1.2 M, can be generally similar to those described
herein. In embodiments, other types of salts can be added to the
electrolyte.
[0027] The sodium concentration in cell 10, e.g., 100-1500 ppm by
weight, can be generally similar to those described herein. Without
wishing to be bound by theory, it is believed that as the
concentration of EC increases, the concentration of sodium can be
increased without substantially affecting cell 10 adversely.
Accordingly, in embodiments, the sodium concentration in cell 10
having EC can be between about 100 ppm to 3,000 ppm by weight. The
sodium concentration can be equal to or greater than 100, 200, 300,
400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1600,
1800, 1900, 2100, 2300, 2500, 2700, or 2900 ppm by weight; and/or
equal to or less than 2900, 2700, 2500, 2300, 2100, 1900, 1800,
1600, 1500, 1400, 1300, 1200, 1100, 1000, 900, 800, 700, 600, 500,
400, 300, 200, or 100 ppm by weight.
[0028] Cathode 16 includes an active cathode material, which is
generally coated on the cathode current collector. The current
collector is generally titanium, stainless steel, nickel, aluminum,
or an aluminum alloy, e.g., aluminum foil. The active material can
be, e.g., a metal oxide, halide, or chalcogenide; alternatively,
the active material can be sulfur, an organosulfur polymer, or a
conducting polymer. Specific examples include MnO.sub.2,
V.sub.2O.sub.5, CoF.sub.3, MoS.sub.2, FeS.sub.2, SOCl.sub.2,
MoO.sub.3, S, (C.sub.6H.sub.5N).sub.n, (S.sub.3N.sub.2).sub.n,
where n is at least 2. The active material can also be a carbon
monofluoride. An example is a compound having the formula CF.sub.x,
where x is 0.5 to 1.0. The active material can be mixed with a
conductive material such as carbon and a binder such as
polytetrafluoroethylene (PTFE). An example of a cathode is one that
includes aluminum foil coated with MnO.sub.2. The cathode can be
prepared as described in U.S. Pat. No. 4,279,972.
[0029] Anode 12 can consist of an active anode material, usually in
the form of an alkali metal, e.g., Li, K, or an alkaline earth
metal, e.g., Ca, Mg. The anode can also consist of alloys of alkali
metals and alkaline earth metals or alloys of alkali metals and Al.
The anode can be used with or without a substrate. The anode also
can consist of an active anode material and a binder. In this case
an active anode material can include carbon, graphite, an
acetylenic mesophase carbon, coke, a metal oxide and/or a lithiated
metal oxide. The binder can be, for example, PTFE. The active anode
material and binder can be mixed to form a paste that can be
applied to the substrate of anode 12.
[0030] In some embodiments, the sodium content in a lithium anode
is less than about 500 ppm by weight, e.g., less than 400 ppm, less
than 300 ppm, less than 200, or less than 100 ppm. The sodium
content can be controlled by carefully controlling anode processing
(e.g., lithium extrusion), cell processing, cell aging, cell
predischarge, cell storage, and/or cell discharge.
[0031] Separator 20 can be formed of any of the standard separator
materials used in nonaqueous electrochemical cells. For example,
separator 20 can be formed of polypropylene (e.g., nonwoven
polypropylene or microporous polypropylene), polyethylene, layers
of polypropylene and polyethylene, and/or a polysulfone.
[0032] To assemble the cell, separator 20 can be cut into pieces of
a similar size as anode 12 and cathode 16 and placed therebetween
as shown in FIG. 1. Anode 12, cathode 16, and separator 20 are then
placed within case 22, which can be made of a metal such as nickel,
nickel plated steel, stainless steel, or aluminum, or a plastic
such as polyvinyl chloride, polypropylene, polysulfone, ABS or a
polyamide. Case 22 is then filled with the electrolytic solution
and sealed. One end of case 22 is closed with a cap 24 and an
annular insulating gasket 26 that can provide a gas-tight and
fluid-tight seal. Positive current collector 18, which can be made
of aluminum, connects cathode 16 to cap 24. Cap 24 may also be made
of aluminum. A safety valve 28 is disposed in the inner side of cap
24 and is configured to decrease the pressure within battery 10
when the pressure exceeds some predetermined value. Additional
methods for assembling the cell are described in U.S. Pat. Nos.
4,279,972; 4,401,735; and 4,526,846.
[0033] Other configurations of battery 10 can also be used,
including, e.g., the coin cell configuration. The batteries can be
of different voltages, e.g., 1.5V, 3.0V, or 4.0V.
[0034] Other embodiments are within the claims.
* * * * *