U.S. patent application number 12/897602 was filed with the patent office on 2011-01-27 for electric current-producing device having sulfone-based electrolyte.
This patent application is currently assigned to Arizona Board of Regents for and on behalf of Arizona State University. Invention is credited to Charles Austen Angell, Xiao-Guang Sun.
Application Number | 20110020712 12/897602 |
Document ID | / |
Family ID | 36692894 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110020712 |
Kind Code |
A1 |
Angell; Charles Austen ; et
al. |
January 27, 2011 |
ELECTRIC CURRENT-PRODUCING DEVICE HAVING SULFONE-BASED
ELECTROLYTE
Abstract
Electrolytic solvents and applications of such solvents
including electric current-producing devices. For example, a
solvent can include a sulfone compound of
R.sup.1--SO.sub.2--R.sup.2, with R.sup.1 being an alkyl group and
R.sup.2 a partially oxygenated alkyl group, to exhibit high
chemical and thermal stability and high oxidation resistance. For
another example, a battery can include, between an anode and a
cathode, an electrolyte which includes ionic electrolyte salts and
a non-aqueous electrolyte solvent which includes a non-symmetrical,
non-cyclic sulfone. The sulfone has a formula of
R.sup.1--SO.sub.2--R.sup.2, wherein R.sup.1 is a linear or branched
alkyl or partially or fully fluorinated linear or branched alkyl
group having 1 to 7 carbon atoms, and R.sup.2 is a linear or
branched or partially or fully fluorinated linear or branched
oxygen containing alkyl group having 1 to 7 carbon atoms. The
electrolyte can include an electrolyte co-solvent and an
electrolyte additive for protective layer formation.
Inventors: |
Angell; Charles Austen;
(Mesa, AZ) ; Sun; Xiao-Guang; (Knoxville,
TN) |
Correspondence
Address: |
FISH & RICHARDSON P.C. (SD)
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Arizona Board of Regents for and on
behalf of Arizona State University
Scottsdale
AZ
|
Family ID: |
36692894 |
Appl. No.: |
12/897602 |
Filed: |
October 4, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11780416 |
Jul 19, 2007 |
7833666 |
|
|
12897602 |
|
|
|
|
PCT/US2006/001975 |
Jan 19, 2006 |
|
|
|
11780416 |
|
|
|
|
60645536 |
Jan 19, 2005 |
|
|
|
Current U.S.
Class: |
429/340 ; 568/28;
568/35 |
Current CPC
Class: |
H01M 10/0567 20130101;
H01M 2300/0025 20130101; Y02E 60/10 20130101; H01M 6/164 20130101;
H01M 6/168 20130101; H01M 10/0569 20130101; H01M 10/052 20130101;
H01M 2300/0037 20130101; H01G 11/64 20130101; H01G 9/038 20130101;
Y02E 60/13 20130101; H01G 11/60 20130101 |
Class at
Publication: |
429/340 ; 568/28;
568/35 |
International
Class: |
H01M 10/02 20060101
H01M010/02; C07C 317/00 20060101 C07C317/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] The U.S. Government has a paid-up license in the present
invention and the right in limited circumstances to require the
patent owner to license others on fair and reasonable terms as
provided by the terms of Grant No. DEFG039ER14378-003 and
DEFG03945541 awarded by the U.S. Department of Energy.
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2006 |
WO |
PCTUS2006001975 |
Claims
1. A solvent comprising a non-cyclic sulfone of the general
formula: R.sup.1--SO.sub.2--R.sup.2 wherein R.sup.1 is an alkyl
group, and R.sup.2 is an alkyl group that is at least partially
oxygenated.
2. The solvent according to claim 2 wherein R.sup.2 is at least
partially fluorinated.
3. The solvent according to claim 1 wherein R.sup.2 is fully
fluorinated.
4. The solvent according to claim 1 wherein R.sup.1 is at least
partially fluorinated.
5. The solvent according to claim 1 wherein R.sup.1 is fully
fluorinated.
6. The solvent according to claim 2 wherein the non-cyclic sulfone
is non-symmetric.
7. The solvent according to claim 1, wherein R.sup.1 comprises at
least one of: methyl(--CH.sub.3); ethyl(--CH.sub.2CH.sub.3);
n-propyl(--CH.sub.2CH.sub.2CH.sub.3);
n-butyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-pentyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-hexyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-heptyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl(--CH(CH.sub.3).sub.2);
iso-butyl(--CH.sub.2CH(CH.sub.3).sub.2);
sec-butyl(--CH(CH.sub.3)CH.sub.2CH.sub.3);
tert-butyl(--C(CH.sub.3).sub.3);
iso-pentyl(--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2);
trifluoromethyl(--CF.sub.3);
2,2,2-trifluoroethyl(--CH.sub.2CF.sub.3); 1,1-difluoroethyl
(--CF.sub.2CH.sub.3); perfluoroethyl(--CF.sub.2CF.sub.3);
3,3,3-trifluoro-n-propyl(--CH.sub.2CH.sub.2CF.sub.3);
2,2-difluoro-n-propyl(--CH.sub.2CF.sub.2CH.sub.3);
1,1-difluoro-n-propyl(--CF.sub.2CH.sub.2CH.sub.3);
1,1,3,3,3-pentafluoro-n-propyl(--CF.sub.2CH.sub.2CF.sub.3);
2,2,3,3,3-pentafluoro-n-propyl(--CH.sub.2CF.sub.2CF.sub.3);
perfluoro-n-propyl(--CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-butyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-pentyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-hexyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.s-
ub.3); --CF (CH.sub.3).sub.2; --CH(CH.sub.3)CF.sub.3; --CF
(CF.sub.3).sub.2; --CH(CF.sub.3).sub.2;
--CH.sub.2CF(CH.sub.3).sub.2; --CF.sub.2CH(CH.sub.3).sub.2;
--CH.sub.2CH(CH.sub.3)CF.sub.3; --CH.sub.2CH(CF.sub.3).sub.2;
--CF.sub.2CF(CF.sub.3).sub.2; --C(CF.sub.3).sub.3.
8. The solvent according to claim 1, wherein R.sup.2 comprises at
least one of: --CH.sub.2OCH.sub.3; --CF.sub.2OCH.sub.3;
--CF.sub.2OCF.sub.3; --CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2OCH.sub.3; --CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.3; --CF.sub.2CF.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.3; --CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2OCF.sub.3; --CHFCF.sub.2OCF.sub.2H;
--CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3.
9. The solvent according to claim 1, wherein R.sup.1 is at least
partially oxygenated.
10. The solvent according to claim 9 wherein R.sup.1 has a
different formulation than R.sup.2.
11. A device, comprising: an electrolyte comprising: one or more
ionic electrolyte salts; and a solvent comprising a non-cyclic
sulfone of the general formula: R.sup.1--SO.sub.2--R.sup.2 wherein
R.sup.1 is an alkyl group, and R.sup.2 is an alkyl group that is at
least partially oxygenated.
12. The device according to claim 11 wherein R.sup.2 is at least
partially fluorinated.
13. The device according to claim 11 wherein R.sup.2 is fully
fluorinated.
14. The device according to claim 11 wherein R.sup.1 is at least
partially fluorinated.
15. The device according to claim 11 wherein R.sup.1 is fully
fluorinated.
16. The device according to claim 11, wherein R.sup.1 is at least
partially oxygenated.
17. The device according to claim 16 wherein R.sup.1 has a
different formulation than R.sup.2.
18. The device according to claim 11, wherein the ionic electrolyte
salt comprises at least one of MClO.sub.4, MPF.sub.6,
MPF.sub.x(C.sub.nF.sub.2n-1).sub.6-x, MBF.sub.4,
MBF.sub.4-x(C.sub.nF.sub.2n-1).sub.x, MASF.sub.6, MSCN,
MB(CO.sub.2).sub.4, MN(SO.sub.2CF.sub.3).sub.2, and
MSO.sub.3CF.sub.3, or any mixture thereof; where "M" is lithium or
sodium.
19. The device according to claim 11 comprising an electrolyte
co-solvent.
20. The device according to claim 19, wherein the electrolyte
co-solvent comprises at least one of carbonates, N-methyl
acetamide, acetonitrile, symmetric sulfones, sulfolanes,
1,3-dioxolanes, glymes, polyethylene glycols, siloxanes, and
ethylene oxide grafted siloxanes.
21. The device according to claim 11 further comprising an
electrolyte additive.
22. The device according to claim 21 wherein the electrolyte
additive comprises at least one of: vinylene carbonate (VC),
ethylene sulfite (ES), propylene sulfite (PS), fluoroethylene
sulfite (FEC), .alpha.-bromo-.gamma.-butyrolactone, methyl
chloroformate, t-butylene carbonate, 12-crown-4, carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide (SO.sub.3),
acid anhydrides, reaction products of carbon disulfide and lithium,
polysulfide, and other inorganic additives.
23. The device according to claim 11, comprising an anode and a
cathode in contact with the electrolyte to form an electric
current-producing device which produces an electric current.
24. The device according to claim 23 wherein the electric
current-producing device is configured as a voltaic cell.
25. The device according to claim 23 wherein electric
current-producing device is configured as a supercapacitor.
26. The device according to claim 11, wherein the electrolyte is
configured to exhibit high oxidation resistance.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present non-provisional patent application is a
divisional application of and claims priority to U.S. application
Ser. No. 11/780,416 filed on Jul. 19, 2007 entitled "ELECTRIC
CURRENT-PRODUCING DEVICE HAVING SULFONE-BASED ELECTROLYTE," now
allowed, which is, under 35 U.S.C. .sctn.120, a continuing patent
application of and claims priority to a co-pending PCT Application
No. PCT/US2006/001975 entitled "ELECTRIC CURRENT-PRODUCING DEVICE
HAVING SULFONE-BASED ELECTROLYTE" and filed on Jan. 19, 2006 (PCT
Publication No. WO2006078866(A2)) which, under 35 U.S.C.
.sctn.119(e) (1), claims priority to a U.S. provisional application
Ser. No. 60/645,536 entitled "NEW SULFONE ELECTROLYTES FOR
RECHARGEABLE LITHIUM BATTERIES" and filed on Jan. 19, 2005 by
Xiao-Guang Sun et al.
[0002] The above referenced prior patent applications are
incorporated by reference in their entirety as part of the
specification of the present application.
TECHNICAL FIELD
[0004] The present specification relates to electric
current-producing devices and techniques including non-aqueous
electrolyte solvents for use in electric current-producing
devices.
BACKGROUND
[0005] Batteries are commonly used to power many types of motors
and electronic devices for use in portable applications. The
battery may be rechargeable or disposable (one-shot usage) type.
The battery provides operating power for integrated circuits in
portable electronic systems, or provides an electromotive force to
drive motors for industrial applications.
[0006] One area of particular interest is automotive power trains.
Battery-powered automobiles offer many interesting possibilities
for fulfilling transportation needs, while reducing energy
consumption, and minimizing hazard to the environment. Automobile
batteries must be rechargeable and preferably deliver high
voltages, e.g. greater than 4.5 VDC, to provide adequate power to
the motor. The battery should also have good electrochemical
stability, safety and longevity.
[0007] Common types of rechargeable battery are known as
lithium-ion cell and lithium metal cell. U.S. Pat. Nos. 5,460,905;
5,462,566; 5,582,623; and 5,587,253 describe the basic elements and
performance requirements of lithium batteries and their components.
A key issue in the development of high energy batteries is the
choice of the electrolyte element to improve the possible output
voltage, stability, cycle life, and safety of the battery. A large
number of non-aqueous organic solvents have been suggested and
investigated as electrolytes in connection with various types of
cells containing lithium electrodes. U.S. Pat. Nos. 3,185,590;
3,578,500; 3,778,310; 3,877,983; 4,163,829; 4,118,550; 4,252,876;
4,499,161; 4,740,436; and 5,079,109 describe many possible
electrolyte element combinations and electrolyte solvents, such as
borates, substituted and unsubstituted ethers, cyclic ethers,
polyethers, esters, sulfones, alkylene carbonates, organic
sulfites, organic sulfates, organic nitrites and organic nitro
compounds.
[0008] One class of organic electrolyte solvents that has received
attention as a component of electrolyte elements for
electrochemical cells and other devices are the sulfones. Sulfones
can generally be divided into two types: the aromatic sulfones and
the aliphatic sulfones. The aliphatic sulfones can also be divided
into two types--the cyclic (commonly referred to as sulfolanes) and
non-cyclic. The non-cyclic aliphatic sulfones form a
potentially-attractive group of organic solvents that present a
high chemical and thermal stability.
[0009] In particular, ethyl methyl sulfone (EMS) has shown
remarkable electrochemical stability, reaching 5.8 V vs.
Li/Li.sup.+ by a conservative stability criterion. For example, 2M
LiPF.sub.6/EMS has been used as the supporting electrolyte in a
dual graphite cell which operates around 5.5 V, and 1M
LiPF.sub.6/EMS has been used as the electrolyte in
Li/T.sub.2--Li.sub.2/3[Ni.sub.1/3Mn.sub.2/3]O.sub.2 cell which
operates up to 5.4 V. Despite its success as solvent in those
cases, EMS applications are limited by a shortcoming, i.e. its
relatively high melting point, 36.5.degree. C., which eliminates
its use as a single solvent in electronic devices whose range of
operation includes temperatures much below ambient. To overcome
this limitation EMS must be blended with other high stability
solvents that yield low-melting eutectics with EMS, or be replaced
by alternative sulfones with lower melting points.
[0010] A eutectic mixture of EMS with dimethyl sulfone melts at
25.degree. C., and the mixture has been used in lithium salt
solution conductivity studies extending well below ambient,
however, crystallization takes place on long exposure to low
temperatures. Since single solvent electrolytes are desirable for a
variety of reasons, and since alternative second components to
provide lower-melting eutectics than the above are also desirable,
a need exists to further study the synthesis of sulfone-containing
molecular liquids.
SUMMARY
[0011] In one embodiment, the present specification discloses an
electrolyte element for use in an electric current-producing device
comprising one or more ionic electrolyte salts and a non-aqueous
electrolyte solvent including one or more non-symmetrical,
non-cyclic sulfones of the general formula:
R.sup.1--SO.sub.2--R.sup.2. The R.sup.1 group is a linear or
branched alkyl or partially or fully fluorinated linear or branched
alkyl group having 1 to 7 carbon atoms. The R.sup.2 group, which is
different in formulation than the R.sup.1 group, is a linear or
branched or partially or fully fluorinated linear or branched
oxygen containing alkyl group having 1 to 7 carbon atoms.
[0012] In another embodiment, the present specification discloses
an electric current-producing device comprising a cathode and an
anode. A non-aqueous electrolyte element is disposed between the
cathode and anode. The non-aqueous electrolyte element includes an
electrolyte salt and a non-symmetrical, non-cyclic sulfone of the
general formula: R.sup.1--SO.sub.2--R.sup.2. R.sup.1 is an alkyl
group, and R.sup.2 is an alkyl group including oxygen.
[0013] In another embodiment, the present specification discloses
an electrolyte for an electric current-producing device comprising
a non-aqueous electrolyte solvent including a non-symmetrical,
non-cyclic sulfone of the general formula:
R.sup.1--SO.sub.2--R.sup.2. R.sup.1 is an alkyl group, and R.sup.2
is an alkyl group including oxygen.
[0014] In another embodiment, the present specification discloses a
method of forming an electric current-producing device, comprising
the steps of providing a cathode, providing an anode, and providing
a non-aqueous electrolyte element disposed between the cathode and
anode. The non-aqueous electrolyte element includes an electrolyte
salt and a non-symmetrical, non-cyclic sulfone of the general
formula: R.sup.1--SO.sub.2--R.sup.2. R.sup.1 is an alkyl group, and
R.sup.2 is an alkyl group including oxygen.
[0015] In yet another embodiment, the present specification
discloses an electrolytic solvent comprising a sulfone compound and
being configured to exhibit high chemical and thermal stability and
high oxidation resistance. Such a sulfone may be represented by a
chemical formula of: R.sup.1--SO.sub.2--R.sup.2 wherein R.sup.1 is
an alkyl group and R.sup.2 is a partially oxygenated alkyl group.
This electrolytic solvent may be combined with ionic salts,
co-solvents, or other additives and may be used as an electrolyte
element in an electric current-producing device. This sulfone-based
electrolyte can be used in an electric current-producing device to
generate high output voltages and maintain high oxidation
resistance. Therefore, such a sulfone-based electrolyte can be
implemented in electrolytic cells, rechargeable batteries, electric
capacitors, fuel cells, and the like which comprise non-aqueous
electrolyte elements to provide high energy storage capacity, long
cycle life, and a low rate of self-discharge, with good thermal
stability.
[0016] In yet another implementation, the present specification
provides an electrolyte solvent of the formula:
R.sup.1--SO.sub.2--R.sup.2, wherein R.sup.1 and R.sup.2 are alkyl
groups that are at least partially oxygenated. Such a solvent can
be used in electric current-producing devices and other
devices.
[0017] In yet another implementation, the present specification
provides an electrolyte solvent of the formula:
R.sup.1--SO.sub.2--R.sup.2, wherein R.sup.1 is an alkyl group,
R.sup.2 is an alkyl group that is at least partially oxygenated,
and R.sup.1, R.sup.2, or both are partially or fully fluorinated.
Such a solvent can be used in an electric current-producing devices
and other devices
[0018] In yet another implementation, the present specification
provides an electrolyte comprising one or more ionic electrolyte
salts and a solvent of the formula: R.sup.1--SO.sub.2--R.sup.2,
wherein R.sup.1 is an alkyl group and R.sup.2 is an alkyl group
that is at least partially oxygenated. Such an electrolyte can be
used in an electric current-producing devices and other devices
[0019] Various features described in the present specification can
be used to provide an electrolyte solution which combines high
oxidation resistance and high ambient temperature conductivity, an
electrolyte solution which exhibits exceptionally high conductivity
and high chemical and electrochemical stability. An electrolyte
solvent described in the present specification may also be combined
with one or more ionic salts, one or more liquid co-solvents,
gelling agents, ionically conductive solid polymers, and other
additives.
[0020] These and other embodiments and implementations are
described in detail in the drawing, the description and the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates a lithium battery providing power to a
load;
[0022] FIG. 2 illustrates non-symmetrical, non-cyclic sulfone group
coupled with a R.sup.1 alkyl group and R.sup.2 oxygen containing
alkyl group;
[0023] FIG. 3 is a graph of conductivities of 1M LiTFSI in
different sulfones;
[0024] FIGS. 4a-4b are graphs of electrochemical stability ranges
("windows") for 1M LiTFSI in different sulfone solutions;
[0025] FIG. 5 is a graph of performance of the cell MCMB25-28|1M
LiPF.sub.6/EMES|Li under the current density of 0.013
mA/cm.sup.2;
[0026] FIGS. 6a-6b are graphs of cell performance under different
current densities;
[0027] FIG. 7 is a graph of charge/discharge capacity and coulomb
efficiency of the cell LiCr.sub.0.015Mn.sub.1.985O.sub.4|1M
LiPF.sub.6/EMES|Li under the current density of 0.092
mA/cm.sup.2;
[0028] FIGS. 8a-8b are graphs of charge and discharge profile of
half cell of Li.parallel.Graphite and full cell of
Graphite.parallel.LiCoO.sub.2 using 1.0M LiPF.sub.6/EMES as the
electrolyte, respectively;
[0029] FIGS. 9a-9b are graphs of temperature dependence of ionic
conductivities of 1.0M lithium salts, A) 1.0M lithium salts in EMES
containing 5 wt % carbonates (EC and DMC) and ethylene sulfite
(ES); B) 1.0M LiPF.sub.6 in EMES containing different percentage of
EC;
[0030] FIGS. 10a-10d are graphs of cyclic voltammograms for 1M
LiPF.sub.6 in different EMES/EC mixtures, A) 5 wt % EC; B) 10 wt %
EC; C) 20 wt % EC; D) 30 wt % EC;
[0031] FIGS. 11a-11d are graphs of cyclic voltammograms for 1M
LiPF.sub.6 in different EMES/DMC mixtures, A) 5 wt % DMC; B) 10 wt
% DMC; C) 20 wt % DMC; D) 30 wt % DMC;
[0032] FIG. 12 is a graph of a first lithium intercalation and
de-intercalation profile on graphite electrode using different 1.0M
LiPF.sub.6 electrolyte solutions;
[0033] FIG. 13 is a graph of a first charge and discharge profile
of full cell of graphite.parallel.LiCoO.sub.2 using different 1.0M
LiPF.sub.6 electrolyte solutions; and
[0034] FIG. 14 is a graph of an electrochemical window for 1M
LiClO.sub.4 in EMES/ES mixture.
DETAILED DESCRIPTION
[0035] The present invention is described in one or more
embodiments in the following description with reference to the
Figures, in which like numerals represent the same or similar
elements. While the invention is described in terms of the best
mode for achieving the invention's objectives, it will be
appreciated by those skilled in the art that it is intended to
cover alternatives, modifications, and equivalents as may be
included within the spirit and scope of the invention as defined by
the appended claims and their equivalents as supported by the
following disclosure and drawings.
[0036] Batteries are commonly used to power many types of
electronics, motors, and other devices for use in portable
applications. The battery may be rechargeable or disposable
one-shot usage type. The battery provides operating power for
integrated circuits in portable electronic systems, or an
electromotive force to drive motors for industrial and automotive
applications.
[0037] FIG. 1 illustrates electric current-producing device 10
providing electrical power to load 12. In one embodiment, the
electric current-producing device 10 is a battery or other voltaic
cell. Alternatively, the electric current-producing device 10 is a
supercapacitor. Device 10 may include a lithium-ion cell or lithium
metal cell, or plurality of such cells. Device 10 has anode 14,
cathode 16, and electrolyte 18. Anode 14 and cathode 16 are
connected to load 12 to provide electrical power to the load.
Electrolyte 18 contains a non-aqueous electrolyte element
comprising a non-symmetrical, non-cyclic sulfone component, as
described fully hereinafter, that is stable in the presence of the
anode and cathode. Load 12 may be an electronic system, equipment
in an industrial application, or motor for an automobile, just to
name a few.
[0038] The material of anode 14 has one or more metals or metal
alloys selected from the Group IA and IIA metals in the Periodic
Table. For example, anode 14 may be made with lithium or sodium.
The anode may also be alkali-metal intercalated carbon, such as
LiC.sub.x where x is equal to or greater than 2. Also useful as
anode materials are alkali-metal intercalated conductive polymers,
such as lithium, sodium or potassium doped polyacetylenes,
polyphenylenes, polyquinolines, and the like. Examples of other
suitable anode material are lithium metal, lithium-aluminum alloys,
lithium-tin alloys, lithium-intercalated carbons,
lithium-intercalated graphites, calcium metal, aluminum, sodium,
and sodium alloys.
[0039] Cathode 16 may be made with any of the commonly used cathode
active materials. Examples of suitable cathode active materials are
inorganic insertion oxides and sulfides, metal chalcogenides,
elemental sulfur, organo-sulfur and carbon-sulfur polymers,
conjugated polymers, and liquid cathodes. Useful inorganic
insertion oxides include CoO.sub.2, NiO.sub.2, MnO.sub.2,
Mn.sub.2O.sub.4, V.sub.6O.sub.13, V.sub.2O.sub.5, and blends
thereof. Useful inorganic sulfides include TiS.sub.2, MoS.sub.2,
and the like. Suitable conjugated polymers include polyacetylene,
poly(phenylene vinylene), and polyaniline. Useful liquid cathodes
include SO.sub.2, SOCl.sub.2, SO.sub.2Cl.sub.2, and POCl.sub.3.
Useful organo-sulfur materials include those disclosed in U.S. Pat.
Nos. 4,833,048; 4,917,974; 5,324,599; and 5,516,598.
[0040] Further examples of useful cathode active materials include
organo-sulfur polymer materials, as described in U.S. Pat. No.
5,441,831, and carbon-sulfur materials, as described in U.S. Pat.
Nos. 5,601,947 and 5,529,860. Sulfur containing cathode active
organic materials as described in these disclosures comprise, in
their oxidized state, a polysulfide moiety of the formula,
--S.sub.m--, wherein m is an integer equal to or greater than 3.
Further useful composite cathode compositions including
organo-sulfur or elemental sulfur. Cathode 16 may further comprise
one or more materials which include: binders, electrolytes, and
conductive additives, usually to improve or simplify their
fabrication as well as improve their electrical and electrochemical
characteristics.
[0041] Useful conductive additives are those known to one skilled
in the art of electrode fabrication and are such that they provide
electrical connectivity to the majority of the electroactive
materials in the composite cathode. Examples of useful conductive
fillers include conductive carbons (e.g., carbon black), graphites,
metal flakes, metal powders, electrically conductive polymers, and
the like.
[0042] In those cases where binder and conductive filler are
desired, the amounts of binder and conductive filler can vary
widely and the amounts present will depend on the desired
performance. Typically, when binders and conductive fillers are
used, the amount of binder will vary greatly, but will generally be
less than about 15 wt % of the composite cathode. The amount of
conductive filler used will also vary greatly and will typically be
less than 20 wt % of the composite cathode. Useful amounts of
conductive additives are generally less than 12 wt %.
[0043] The choice of binder material may vary widely so long as it
is inert with respect to the composite cathode materials. Useful
binders are those materials, usually polymeric, that allow for ease
of processing of battery electrode composites. Examples of useful
binders are organic polymers such as polytetrafluoroethylenes
(TEFLON.TM.), polyvinylidine fluorides (PVF.sub.2 or PVDF),
ethylene-propylene-diene (EPDM) rubbers, polyethylene oxides (PEO),
UV curable acrylates, UV curable methacrylates, and UV curable
divinylethers, and the like.
[0044] For the case of the automotive application, battery-powered
motors offer many interesting possibilities for fulfilling
transportation needs with greater efficiency and reduced harm to
the environment. Automobile batteries must be rechargeable and
preferably deliver high voltages, e.g. greater than 4.5 VDC, to
provide adequate power to the motor. The battery should also have
good electrochemical stability and longevity. Electrolyte 18 plays
an important role in the electrochemical performance of electric
current-producing device 10, including the ability to generate high
output voltages for maximum power transfer.
[0045] Electrolyte elements are useful in electrolytic cells,
rechargeable batteries, electric capacitors, fuel cells, and
function as a medium for storage and transport of ions. The term
"electrolyte element," as used herein, relates to an element of an
electric current-producing device which comprises an electrolyte
solvent, one or more electrolyte salts, and optionally other
additives including polymer electrolytes and gel-polymer
electrolytes. Any liquid, solid, or solid-like material capable of
storing and transporting ions may be used, so long as the material
is chemically inert with respect to anode 14 and cathode 16, and
the material facilitates the transportation of ions between the
anode and the cathode. In the special case of solid electrolytes,
these materials may additionally function as separator materials
between the anode and cathode.
[0046] The electrolyte elements of the present invention include
one or more ionic electrolyte salts and a non-aqueous electrolyte
solvent. The non-aqueous electrolyte solvent contains one or more
non-symmetrical, non-cyclic sulfones, and optionally other
additives, such as one or more electrolyte co-solvents, gelling
agents, ionically conductive solid polymers, and/or other
additives. The electrolyte elements may be prepared by dissolving
one or more ionic electrolyte salts in one or more non-aqueous
electrolyte solvents.
[0047] As a feature of the present invention, a new sulfone is
introduced into the composition of electrolyte 18. The sulfones are
provided in the battery electrolyte to increase the possible output
voltage and available power from the battery. In particular,
sulfones with different length of oligo ethylene glycol segments
have been synthesized and tested for use in rechargeable lithium
batteries. Relative to the model compound EMS, which has a melting
point of 36.5.degree. C., the new sulfones have low melting points,
mostly depressed below room temperature. Their conductivities are
lower than that of EMS. The highest ambient temperature
conductivity of 10.sup.-2.58 Scm.sup.-1 is obtained for 0.7M
LiTFSI/MEMS solution. The sulfones show wide electrochemical
stability windows, in excess of 5.0 V vs Li/Li.sup.+, increasing
with decreasing length of the oligoether chains. A cell with
lithium metal anode and manganate cathode performed well,
maintaining high coulomb efficiency over 200 cycles.
[0048] The non-aqueous electrolyte solvents include a
non-symmetrical, non-cyclic sulfone, suitable for use in electric
current-producing devices, such as device 10. As shown in FIG. 2,
the non-symmetrical, non-cyclic sulfone has the general formula:
R.sup.1--SO.sub.2--R.sup.2. The SO.sub.2 group 20 represents the
sulfone group. The R.sup.1 group 22 is a linear or branched alkyl
or partially or fully fluorinated linear or branched alkyl group
having 1 to 7 carbon atoms. The R.sup.2 group 24 is a linear or
branched or partially or fully fluorinated linear or branched alkyl
group containing oxygen and having 1 to 7 carbon atoms. In another
embodiment, the R.sup.1 and R.sup.2 groups each have 1 to 4 carbon
atoms.
[0049] The SO.sub.2 sulfone group is the same group that occurs in
the following compounds: ethylmethyl sulfone (EMSF,
CH.sub.3CH.sub.2--SO.sub.2--CH.sub.3), ethyl-iso-propyl sulfone
(EiPSF, CH.sub.3CH.sub.2--SO.sub.2--CH(CH.sub.3).sub.2),
ethyl-sec-butyl sulfone (EsBSF,
CH.sub.3CH.sub.2--SO.sub.2--CH(CH.sub.3) (CH.sub.2CH.sub.3)),
ethyl-iso-butyl sulfone (EiBSF).
[0050] Examples of the R.sup.1 alkyl group are: methyl(--CH.sub.3);
ethyl(--CH.sub.2CH.sub.3); n-propyl(--CH.sub.2CH.sub.2CH.sub.3);
n-butyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-pentyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-hexyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
n-heptyl(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl(--CH(CH.sub.3).sub.2);
iso-butyl(--CH.sub.2CH(CH.sub.3).sub.2);
sec-butyl(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl
(--C(CH.sub.3).sub.3);
iso-pentyl(--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3); 2,2,2-trifluoroethyl(--CH.sub.2CF.sub.3);
1,1-difluoroethyl (--CF.sub.2CH.sub.3);
perfluoroethyl(--CF.sub.2CF.sub.3); 3,3,3-trifluoro-n-propyl
(--CH.sub.2CH.sub.2CF.sub.3);
2,2-difluoro-n-propyl(--CH.sub.2CF.sub.2CH.sub.3);
1,1-difluoro-n-propyl(--CF.sub.2CH.sub.2CH.sub.3);
1,1,3,3,3-pentafluoro-n-propyl (--CF.sub.2CH.sub.2CF.sub.3);
2,2,3,3,3-pentafluoro-n-propyl(--CH.sub.2CF.sub.2CF.sub.3);
perfluoro-n-propyl(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-pentyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-hexyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.s-
ub.3); --CF(CH.sub.3).sub.2; --CH(CH.sub.3)CF.sub.3;
--CF(CF.sub.3).sub.2; --CH(CF.sub.3).sub.2;
--CH.sub.2CF(CH.sub.3).sub.2; --CF.sub.2CH(CH.sub.3).sub.2;
--CH.sub.2CH(CH.sub.3)CF.sub.3; --CH.sub.2CH(CF.sub.3).sub.2;
--CF.sub.2CF(CF.sub.3).sub.2; --C(CF.sub.3).sub.3.
[0051] Examples of the R.sup.2 oxygen containing alkyl group are:
--CH.sub.2OCH.sub.3; --CF.sub.2OCH.sub.3; --CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2OCH.sub.3; --CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.3; --CF.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2OCF.sub.3; --CF.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.3; --CH.sub.2CH.sub.2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H; --CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3.
[0052] In an alternate embodiment, the R.sup.1 alkyl group may also
contain oxygen, e.g. using any one of the formulations described
for the R.sup.2 group. However, the R.sup.1 and R.sup.2 groups will
each have a different formulation from the other, e.g. in terms of
chemical structure or length of segments.
[0053] One group of electrolyte salts includes MClO.sub.4,
MPF.sub.6, MPF.sub.x (C.sub.nF.sub.2n+1).sub.6-x, MBF.sub.4,
MBF.sub.4-x(C.sub.nF.sub.2n-1).sub.x, MASF.sub.6, MSCN,
MB(CO.sub.2).sub.4 ("LiBOB"), and MSO.sub.3CF.sub.3 where "M"
represents lithium or sodium. Also available are electrolyte
solutions including MN(SO.sub.2CF.sub.3).sub.2 as the electrolyte
salt, which exhibits exceptionally high conductivity combined with
high chemical and electrochemical stability.
[0054] The electrolyte elements may further include one or more
liquid electrolyte co-solvents (i.e., in addition to a
non-symmetrical, non-cyclic sulfone), gelling agents, ionically
conductive solid polymers, and other additives. Suitable
electrolyte co-solvents, gelling agents or ionically conductive
solid polymers include any of those commonly used with lithium
metal and lithium-ion cells. For example, suitable liquid
electrolyte co-solvents for use in the electrolyte elements include
any one of the commonly used electrolyte solvents. Examples of
useful liquid electrolyte co-solvents include carbonates, N-methyl
acetamide, acetonitrile, symmetric sulfones, sulfolanes,
1,3-dioxolanes, glymes, polyethylene glycols, siloxanes, and
ethylene oxide grafted siloxanes, and blends thereof. Examples of
useful carbonates include ethylene carbonate (EC) and propylene
carbonate (PC). Examples of useful glymes includes
tetraethyleneglycol dimethyl ether (TEGDME) and
1,2-dimethoxyethane.
[0055] Liquid electrolyte elements are often used in combination
with one of the common porous separators. Liquid electrolyte
solvents or plasticizing agents are often themselves useful as gel
forming agents for gel-polymer electrolytes. Examples of gelling
agents which are useful in the electrolyte elements are those
prepared from polymer matrices derived from polyethylene oxides
(PEO), polypropylene oxides, polyacrylonitriles, polysiloxanes,
polyimides, polyethers, sulfonated polyimides, perfluorinated
membranes (Nafion.TM. resins), polyethylene glycols, polyethylene
glycol-bis-(methyl acrylates), polyethylene glycol-bis(methyl
methacrylates), derivatives of the foregoing, copolymers of the
foregoing, crosslinked and network structures of the foregoing,
blends of the foregoing, and the like.
[0056] Examples of ionically conductive solid polymers suitable for
use in the electrolyte elements are those having polyethers,
polyethylene oxides (PEO), polyimides, polyphosphazenes,
polyacrylonitriles (PAN), polysiloxanes, polyether grafted
polysiloxanes, derivatives of the foregoing, copolymers of the
foregoing, crosslinked and network structures of the foregoing, and
blends of the foregoing, to which is added an appropriate ionic
electrolyte salt. Ionically conductive solid polymers electrolytes
may additionally function as separator materials between the anode
and cathode.
[0057] Other additives which are useful in the electrolyte elements
include soluble additives, such as: vinylene carbonate (VC),
ethylene sulfite (ES), propylene sulfite (PS), fluoroethylene
sulfite (FEC), .alpha.-bromo-.gamma.-butyrolactone, methyl
chloroformate, t-butylene carbonate, 12-crown-4, carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide and other
inorganic additives; acid anhydrides to reduce or eliminate the
presence of water; reaction products of carbon disulfide and
lithium, possibly a soluble sulfide, as disclosed in U.S. Pat. No.
3,532,543; high concentrations of water as described in U.S. Pat.
Nos. 5,432,425 and 5,436,549; and polysulfide additives.
[0058] The non-aqueous electrolyte solvents are particularly useful
in electrolytic cells, rechargeable batteries, electric capacitors,
fuel cells, and the like, which comprise non-aqueous electrolyte
elements and which require high energy storage capacity, long shelf
life, and a low rate of self-discharge. The electrolyte solvents
are particularly useful in electrolytic cells comprising
alkali-metal-containing electrodes, and particularly to lithium
intercalation electrodes.
[0059] The high oxidation resistance of the ambient temperature
electrolyte solutions of the present invention result from the
stability of the --SO.sub.2-- group when in a non-cyclic,
non-symmetric sulfone structure, characterized by freezing
temperatures low enough to enable utilization in ambient
temperature applications. When such a sulfone is utilized as a
solvent to dissolve inorganic electrolyte salts of highly oxidation
resistant anions such as ClO.sub.4, CF.sub.3SO.sub.3 (triflate),
and in particular, bis(trifluoromethane sulfonyl) imide
(--N(CF.sub.3SO.sub.2).sub.2, lithium imide), then solutions which
combine exceptional oxidation resistance with high ambient
temperature conductivity are obtained as, for example, shown in
FIG. 3. In general, FIG. 3 illustrates the DC electrical
conductivities of electrolytes of various solutions of alkali metal
salts in sulfones. As seen in the figure, at 25.degree. C. the
conductivity of EMS is more than half order of magnitude higher
than those of the oligoether sulfones of the present work,
indicating the great advantage of EMS as a single solvent in the
sulfone family.
[0060] The process of making, using, and testing electric
current-producing device 10, including anode 14, cathode 16, and
electrolyte 18 containing the non-aqueous electrolyte solvents
having non-symmetrical, non-cyclic sulfone groups defined above by
R.sup.1--SO.sub.2--R.sup.2 is now described in detail.
[0061] Oligoether-containing sulfides were synthesized by reacting
halide compounds of oligoethylene glycols with sodium
methanethiolate or with sodium ethanethiolate. Sulfones with
structures listed in Table 1 were obtained by oxidation of the
synthesized sulfides with H.sub.2O.sub.2. Table 1 is summary of
physical properties of synthesized sulfones, wherein note.sup.1 is
estimated melting point, note.sup.2 is boiling point under
atmosphere pressure estimated by nomograph, and note.sup.3 is
estimated boiling point.
TABLE-US-00001 TABLE 1 mp T.sub.g Sulfones (.degree. C.)
bp(.degree. C.) (.degree. C.) CH.sub.3CH.sub.2SO.sub.2CH.sub.3
(EMS) 36.5 85~87/4.0 mm -- (~240).sup.2
CH.sub.3OCH.sub.2CH.sub.2SO.sub.2CH.sub.3 (MEMS) 15.0 96~98/1.0 mm
-89.5 (~275).sup.2 CH.sub.3OCH.sub.2CH.sub.2SO.sub.2C.sub.2H.sub.5
(EMES) 2.0 103~105/1.0 mm -91.0 (~286).sup.2
CH.sub.3(OCH.sub.2CH.sub.2).sub.2SO.sub.2C.sub.2H.sub.5 (EMEES)
<0.sup.1 >290.sup.3 -87.6
CH.sub.3(OCH.sub.2CH.sub.2).sub.3SO.sub.2C.sub.2H.sub.5 <0.sup.1
>290.sup.3 -82.5 (EMEEES)
CH.sub.3OCH.sub.2CH.sub.2SO.sub.2CH.sub.2CH.sub.2OCH.sub.3 47.0
>290.sup.3 -90.7 (DMES)
[0062] Glass transition temperature T.sub.g was measured using a
DTA instrument. The heating rate was 10K/min. T.sub.g was defined
as the onset temperature of the heat capacity jump and T.sub.m was
defined as the temperature at which the melting peak reaches its
maximum. The boiling point was recorded during the distillation
process.
[0063] Electrolyte solutions of different salt concentrations were
prepared by dissolving calculated amount of lithium salts in the
respective sulfones. The measurement of DC conductivity was carried
out using an automated frequency impedance analyzer. The
measurements were made automatically during heating of the
pre-cooled samples at 1K/min by means of a programmed controller.
To determine electrochemical characteristics, cyclic voltammetry
was performed using a potentiostat/galvanostat with a
three-electrode cell. The working electrode was a platinum wire,
and the counter and reference electrodes were lithium foil in the
voltage range of -0.3-6.0 V. Most scans were made at room
temperature at a typical scan rate of 1 mV/s.
[0064] Electrochemical half cells, Li.parallel.sulfone
electrolyte.parallel.MCMB25-28 (MCMB for mesocarbon microbeads),
and Li.parallel.sulfone
electrolyte.parallel.LiCr.sub.0.015Mn.sub.1.985O.sub.4 were
constructed using fiberglass paper as the separator. The cathode
solution having 82% active material, 10% carbon black and 8% PVdF
in N-methylpyrrolindone was cast directly on the pre-weighed
stainless steel electrode. The electrode was dried, first at room
temperature and then at 100.degree. C. under vacuum for two days.
The weight of the electrode was determined inside the dry box, and
the weight of active material obtained by difference. The anode
composite electrodes were made in a similar way from a slurry of
90% MCMB25-28 and 10% PVdF in N-methylpyrrolindone. The cell
construction and the tests were all carried out in an argon-filled
glove box. The voltage profile of the charge/discharge process was
monitored using a battery cycler. A constant current ranging from
0.01.about.0.1 mA/cm.sup.2 was used with pre-set cut-off voltage of
0.01.about.2.0 V for Li.parallel.electrolyte.parallel.MCMB25-28
cell and 3.0.about.4.3 V for
Li.parallel.electrolyte.parallel.LiCr.sub.0.015Mn.sub.1.985O.sub.4
cell. At these cut-off voltages a computerized cycler automatically
switched the test cells to charge or discharge.
[0065] All of the ether fragment additions caused the lowering of
melting point relative to EMS except for one case (dimethoxyethyl
sulfone) in which symmetry was retained. Indeed, in some cases
crystallization was not observed at all. For instance, introduction
of the smallest fragment, the methoxy group, at the ethyl end of
EMS yielding methoxyethylmethyl sulfone (MEMS), lowers the melting
point to 15.degree. C. The subambient melting of the compound
formed by adding the same group to the symmetric dimethyulsulfone
(DMS) (mp=110.degree. C.) yielding methoxymethylmethyl-sulphone
(MMMS), the change in melting point being 90K. Attaching the
methoxy group to one end of the symmetric diethyl sulfone (DES)
gives ethyl methoxy ethyl sulfone (EMES) with an even lower melting
point, 2.degree. C., vs 74.degree. C. for the symmetric compound.
These data, along with data for several other variants, are
summarized in Table 1.
[0066] The glass transition temperatures of the new sulfones are
described as follows. For the mono asymmetric sulfones such as
EMES, EMEES (ethyl methoxyethoxyethyl sulfone) and EMEEES (ethyl
methoxyethoxyethoxyethyl sulfone), the glass transition temperature
increases with increasing ether chain length, see Table 1, implying
that the increasing molecular weight effect offsets the decrease in
T.sub.g expected from the dilution of the cohesive sulfone
groups.
[0067] The ionic conductivities, at any temperature, follow the
order: EMS>MEMS>EMES>DMES>EMEES>EMEEES, and appear
to follow the order of the respective sulfone viscosities. Of the
possible synthesized sulfones, the room temperature conductivities
of lithium salt solutions of MEMS and EMES are the highest. Since
the difference is not large, and the ease of synthesis and
purification greater in the case of EMES, the latter is adopted for
making solutions for the electrochemical stability and cell
performance tests.
[0068] In FIGS. 4a-4b, the cyclic voltammetry scans from which the
electrochemical windows for 1.0M LiTFSI solutions at Pt working
electrode under the scan rate of 1 mV/s in EMES, EMEES are
obtained. FIG. 4a shows EMES, while FIG. 4b is EMEES. The cyclic
voltammetry scans are well above 5.0 V vs. Li.sup.+/Li. FIGS. 4a-4b
also show that, with increasing ether chain length, the
electrochemical stability decreases, from 5.6 V for EMES, 5.3 V for
EMEES, (vs 5.9 V for EMS) showing that stability advantage of
sulfone, as a class of solvent, is diminishing with increasing
ether group concentration.
[0069] FIG. 5 shows a test of the ether sulfone-based solutions for
reversible intercalation into the graphite designated MCMB25-28,
for the first three cycles of the cell MCMB25-28|1M
LiPF.sub.6/EMES|Li during cycling at constant current density of
0.013 mA/cm.sup.2. The corresponding charge and discharge
capacities of the first three cycles are 343.0, (202.8); 251.4,
(200.5); 219.2, (193.0) mAh/g, respectively.
[0070] Next, the performance of the new solutions with lithium
metal anodes and Cr.sup.3+-modified LiMn.sub.2O.sub.4 spinel
intercalation cathodes are tested. FIGS. 6a-6b compare the cell
performance using different 1M lithium salts in EMES during the
first cycle under different current densities. FIG. 6a shows data
from the cell using 1M LiTFSI/EMES electrolyte. FIG. 6b shows data
from the cell using 1M LiPF.sub.6/EMES electrolyte. Each cell shows
two well-defined discharge plateaus, around 4.0 and 4.1 V versus
Li/Li.sup.+, respectively. It is also seen that the capacities
decrease with increasing current density.
[0071] When the charge/discharge rates are raised, there is
progressively less time for lithium ions to diffuse through the
LiMn.sub.2O.sub.4 crystallites. At higher rates, only lithium ions
located in the outer regions of the grains are accessible for
reaction, causing a reduction in capacity. However, comparatively
the cell using 1M LiPF.sub.6 electrolyte exhibited a higher
capacity than the cell using 1M LiTFSI/EMES electrolyte under
similar current densities. In addition it has been shown that the
charge/discharge capacities for the cells using LiTFSI/EMES
decreases very quickly with cycling due to its failure to form
effective SEI layers, thus LiPF.sub.6 is useful as the lithium salt
for full cell test. The corresponding cell performance under the
current density of 0.092 mA/cm.sup.2 using 1M LiPF.sub.6/EMES in
terms of charge/discharge capacities and coulomb efficiency is
shown in FIG. 7. This cell showed excellent cyclability, more than
200 cycles, tending to stabilize after 200 cycles at a discharge
capacity around 50 mAh/g and a stable coulomb efficiency around
0.86.
[0072] It is further noted that improved performance may be
obtained when the present hybrid sulfones are mixed with
fluorinated sulfones on the one hand or with alkyl carbonates on
the other. The incorporation of oligoether segments into molecular
sulfones lowers the freezing point to sub-ambient values, without
decreasing the electrochemical window, but may increase the
viscosity with consequent lowering of lithium salt solution
conductivities. However, any decrease in conductivity can be
compensated by fluorination of the R.sup.1 and R.sup.2 alkyl
groups. The oligoether-containing sulfones retain high
electrochemical stability with "windows" well above 5.0 V versus
Li.sup.+/Li. It is possible that Li.sup.+ may be
intercalated/de-intercalated into graphite electrode by using
oligoether-containing sulfones.
[0073] In another embodiment, the novel non-cyclic, non-symmetrical
sulfones are substituted with perfluoromethyl (trifluoromethyl,
--CF.sub.3) or perfluoromethylene(--CF.sub.2) groups. Substitution
of a methyl, --CH.sub.3, group by a perfluoromethyl, --CF.sub.3, is
surprisingly found to advantageously decrease the viscosity of the
sulfone, thereby increasing the conductivity of the electrolyte
solutions and increasing the penetration of the electrolytes into
the cathode and separator in electrolytic cells at ambient
conditions.
[0074] Useful are the novel fluorinated sulfones
CF.sub.3CH.sub.2SO.sub.2CH.sub.3 (2,2,2-trifluoroethylmethyl
sulfone, CF.sub.3MMSF) and CF.sub.3CH.sub.2CH.sub.2SO.sub.2CH.sub.3
(CF.sub.3EMSF). Also available is CF.sub.3MMSF which exhibits very
high conductivity, for example, in lithium chlorate solutions. The
fluorinated non-symmetrical, non-cyclic sulfone further offers
superior wetting, penetration and other surfactant properties.
[0075] Several embodiments of the present invention are described
in the following examples, which are offered by way of illustration
and not by way of limitation.
[0076] In Example 1, involving preparation of methoxyethyl methyl
sulfone (MEMS), 45.6 g thiourea was dissolved in 150 ml water, 28.8
ml dimethyl sulfate was added and the solution was refluxed for 1
hour. After cooling to room temperature, 48 g NaOH in 75 ml
distilled water was added and the solution was stirred for 1 hour,
then 55 g chloroethyl methyl ether (ClCH.sub.2CH.sub.2OCH.sub.3)
was added dropwise. After addition the solution was slowly heated
to reflux for 10 hours. The upper organic layer was separated to
obtain the methoxyethyl methyl sulfide
(CH.sub.3OCH.sub.2CH.sub.2SCH.sub.3) with a yield of 55%. The
sulfide was set to oxidation with 30 wt % H.sub.2O.sub.2 in acetic
acid. On completion of oxidation, most of the solvent was removed.
Dilute NaOH aqueous solution was added to neutralize excess acetic
acid. Water was removed by rotary evaporation and the residual
paste was extracted with chloroform at least three times. The
chloroform was combined and dried over anhydrous sodium sulfate.
Finally chloroform was removed and the crude product was distilled
under vacuum at 95-100.degree. C. to obtain the pure product
MEMS.
[0077] In Example 2, involving preparation of MEMS, a pre-weighed
empty bottle was cooled in dry ice acetone solution and methane
thiol was slowly charged into the bottle. The net weight of
methanethiol was obtained by the difference before and after
weighing as 21.5 g. 71.6 g 25 wt % NaOH aqueous solution was
charged into stainless steel pressure vessel and cooled with ice
water. The vessel was vacuumed and then under stirring methanethiol
was slowly charged into the vessel. The solution was stirred for 1
hr before 38 g chloroethyl methyl ether
(ClCH.sub.2CH.sub.2OCH.sub.3) was added. The solution was stirred
for overnight at room temperature and then heated to reflux for 10
hrs before the process was stopped. The solution was cooled and the
upper organic layer was separated to give a yield of 87%. The
sulfide was then subjected to oxidation with 120 g 30 wt %
H.sub.2O.sub.2 and 100 ml acetic acid. After work up as in Example
1 the crude product was distilled under vacuum and 35 g pure
product was isolated with a yield 71%.
[0078] In Example 3, involving characterization of MEMS, glass
transition temperature T.sub.g was measured using a DTA instrument.
The heating rate used was 10K/min. T.sub.g was defined as the onset
temperature of the heat capacity jump and T.sub.m was defined as
the temperature at which the melting peak reaches its maximum. The
boiling point was recorded during the distillation process. The
T.sub.g and T.sub.m of MEMS are -89.5.degree. C. and 15.degree. C.
respectively, as shown in Table 1. The boiling point of MEMS is
estimated as 275.degree. C. at atmosphere pressure.
[0079] Electrolyte solutions of different salts were prepared by
dissolving calculated amount of lithium salts in MEMS at about
80.degree. C., in the case of LiPF.sub.6 salt the temperature is
controlled around 50.degree. C. The measurement of DC conductivity
was carried out using a frequency impedance analyzer. The
measurements were made automatically during heating of the
pre-cooled samples at 1K/min by means of a programmed controller.
The temperature dependence curve for MEMS containing 1.0M LiTFSI is
shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M different lithium salts in MEMS are shown in
Table 2. In general, Table 2 shows glass transition temperature
(T.sub.g/.degree. C.) and room temperature conductivity
log(.sigma..sub.25/S cm.sup.-1) of 1M different lithium salt
solution in different sulfones.
TABLE-US-00002 TABLE 2 LiTFSI LiSO.sub.3CF.sub.3 LiClO.sub.4
LiBF.sub.4 LiPF.sub.6 LiSCN Sulfone T.sub.g log.sigma..sub.25
T.sub.g log.sigma..sub.25 T.sub.g log.sigma..sub.25 T.sub.g
log.sigma..sub.25 T.sub.g log.sigma..sub.25 T.sub.g
log.sigma..sub.25 EMS -96.0 -2.27 -103.0 -3.00 -110.0 -2.95 -111.0
-2.80 -86.2 -2.55 -101.5 -3.35 MEMS -81.0 -2.83 -83.4 -3.00 -88.0
-2.93 -84.0 -3.03 -82.0 -2.91 -86.5 -3.15 EMES -83.3 -2.85 -87.5
-3.05 -88.0 -3.10 -85.5 -2.89 -88.7 -2.92 -82.5 -3.62 EMEES -73.4
-3.12 -74.0 -3.71 -76.0 -3.39 -76.4 -3.48 -70.4 -3.61 -77.0 -3.92
EMEEES -71.6 -3.25 -68.6 -3.85 -79.4 -3.50 -78.5 -3.55 -77.0 -3.80
-74.6 -3.96 DMES -84.0 -2.99 -83.0 -3.70 -76.4 -3.16 -84.0 -3.30
-82.0 -3.09 -82.5 -3.72
[0080] In Example 4, involving preparation of ethyl methoxyethyl
sulfone (EMES), 57 g NaOH was dissolved in 57 g H.sub.2O and cooled
with ice water, 88.4 g ethanethiol was added to the solution
slowly. The solution was stirred for half hour before 135 g
chloroethyl methyl ether (ClCH.sub.2CH.sub.2OCH.sub.3) was added.
After addition the solution was stirred at room temperature for
several hours before it was heated to reflux for overnight. The
reaction was stopped and cooled to room temperature. Ethyl
methoxyethyl sulfide (CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.3)
in the upper organic layer was separated, 156 g, yield 91%. 100 g
ethyl methoxyethyl sulfide was set up for oxidation with 170 g 50
wt % H.sub.2O.sub.2 and 200 ml acetic acid. After work up as in
Example 1 the crude sulfone was distilled and the fraction at
85-88.degree. C./0.3 Torr was collected.
[0081] In Example 5, involving characterization of EMES, the
T.sub.g and T.sub.m of EMES are -91.0.degree. C. and 2.degree. C.
respectively, as shown in Table 1. The boiling point of MEMS is
estimated as 286.degree. C. at atmosphere pressure. Salt solutions
of EMES were prepared, as described in Example 3, and their ionic
conductivities were measured using the method described in Example
3. The temperature dependence curve for EMES containing 1.0M LiTFSI
is shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMES are shown
in Table 2.
[0082] The cyclic voltammogram of 1M LiTFSI/EMES electrolyte is
recorded at 1.0 mV/s at a Pt working electrode with lithium as both
counter and reference electrode using a potentiostat/galvanostat
instrument, as shown in FIG. 4a.
[0083] In Example 6, involving an electric current-producing device
employing EMES electrolytes, electrochemical half cells,
Li.parallel.sulfone electrolyte.parallel.MCMB25-28, and
Li.parallel.sulfone
electrolyte.parallel.LiCr.sub.0.015Mn.sub.1.985O.sub.4 are
constructed using fiber glass paper as the separator. The cathode
solution having 82% active material, 10% carbon black and 8% PVdF
in N-methylpyrrolindone was cast directly on the pre-weighed
stainless steel electrode. The electrode was dried, first at room
temperature and then at 100.degree. C. under vacuum for two days.
The weight of the electrode was determined inside the dry box, and
the weight of active material obtained by difference. The MCMB25-28
composite electrodes were made in a similar way from slurry of 90%
MCMB25-28 and 10% PVdF in N-methylpyrrolindone.
[0084] Test cells were constructed by using Whatman glass fiber
filter soaked in the electrolyte solution of Example 5 as the
separator and a lithium anode and LiCr.sub.0.015Mn.sub.1.985O.sub.4
(or MCMB25-28) cathode. The tests were all carried out in an
argon-filled glove box. The voltage profile of the charge/discharge
process was monitored using a battery cycler. A constant current
ranging from 0.01.about.0.1 mA/cm.sup.2 was used with pre-set
cut-off voltage of 0.01.about.2.0 V for
Li.parallel.electrolyte.parallel.MCMB25-28 cell and 3.0.about.4.3 V
for
Li.parallel.electrolyte.parallel.LiCr.sub.0.015Mn.sub.1.985O.sub.4
cell respectively. At these cut-off voltages a computerized cycler
automatically switches the test cells to charge or discharge. The
test results are shown in FIGS. 5, 6a-b, and 7, respectively.
[0085] Another set of experiments was performed using commercial
electrode sheets (synthetic graphite and LiCoO.sub.2). The
electrodes are cut into discs with an area of 0.72 cm.sup.2 and
assembled either in a half cell of
Li.parallel.electrolyte.parallel.graphite or full cell of
graphite.parallel.electrolyte.parallel.LiCoO.sub.2. A constant
current density of 0.14 mA/cm.sup.2 was used for both charging and
discharging with pre-set cut-off voltage of 0.01.about.2.0 V for
Li.parallel.electrolyte.parallel.graphite cell and 2.5.about.4.2 V
for graphite.parallel.electrolyte.parallel.LiCoO.sub.2 cell,
respectively. The result is shown in FIGS. 8a-8b.
[0086] In Example 7, involving characterization of mixtures of EMES
with carbonates, the mixtures of EMES with carbonates were prepared
by mixing different weight percentage of either ethylene carbonate
(EC) or dimethyl carbonate (DMC) in EMES. 1.0M LiPF.sub.6
electrolyte solution was prepared by dissolving the salt in the
mixtures at about 50.degree. C., as described in Example 3. The
ionic conductivities were measured using the method described in
Example 3 and their temperature dependence curves are shown in
FIGS. 9a-9b. Addition of EC to the electrolyte solution increases
the ionic conductivities in all cases due to the higher dielectric
constant of EC.
[0087] The cyclic voltammograms of 1M LiPF.sub.6 in EMES/EC and
EMES/DMC were measured, as described in Example 5, and are shown in
FIGS. 10a-10d and 11a-11d, respectively. FIGS. 10a-10d are graphs
of cyclic voltammograms for 1M LiPF.sub.6 in different EMES/EC
mixtures. A) 5 wt % EC; B) 10 wt % EC; C) 20 wt % EC; D) 30 wt %
EC. FIGS. 11a-11d are graphs of cyclic voltammograms for 1M LiPF6
in different EMES/DMC mixtures. A) 5 wt % DMC; B) 10 wt % DMC; C)
20 wt % DMC; D) 30 wt % DMC. Note that the electrochemical
stability windows are all higher than 5.2 V.
[0088] Half cell of Li.parallel.electrolyte.parallel.graphite or
full cell of graphite.parallel.electrolyte.parallel.LiCoO.sub.2
were built using the 1M LiPF.sub.6 electrolytes in EMES/EC and
EMES/DMC, as described in Example 6. A constant current density of
0.14 mA/cm.sup.2 was used for both charging and discharging with
pre-set cut-off voltage of 0.01.about.2.0 V for
Li.parallel.electrolyte.parallel.graphite cell and 2.5.about.4.2 V
for graphite.parallel.electrolyte.parallel.LiCoO.sub.2 cell,
respectively. The results are shown in FIGS. 12 and 13. There is no
graphite exfoliations observed in all the cases studied under the
charge/discharge current density of 0.14 mA/cm.sup.2.
[0089] In Example 8, involving characterization of EMES with
additives, ethylene sulfite (ES) is chosen as an additive and mixed
with EMES at the composition of 5 wt %. 1.0M LiClO.sub.4
electrolyte was prepared by dissolving the salt in the mixture of
EMES/ES at about 80.degree. C., as described in Example 3. The
ionic conductivities were measured using the method described in
Example 3 and its temperature dependence curve shown in FIGS. 9a-9b
is higher than that of 1.0M LiPF.sub.6/EMES solution.
[0090] The cyclic voltammograms of 1M LiClO.sub.4 in EMES/ES was
measured, as described in Example 5, which is shown in FIG. 14. The
electrochemical stability is still higher than 5.0 V.
[0091] Half cell of Li.parallel.electrolyte.parallel.graphite or
full cell of graphite.parallel.electrolyte.parallel.LiCoO.sub.2
were built using the 1M LiCl.sub.4 electrolytes in EMES/ES, as
described in Example 6. A constant current density of 0.14
mA/cm.sup.2 was used for both charging and discharging with pre-set
cut-off voltage of 0.01.about.2.0 V for
Li.parallel.electrolyte.parallel.graphite cell and 2.5.about.4.2 V
for graphite.parallel.electrolyte.parallel.LiCoO.sub.2 cell,
respectively. The results are shown in FIGS. 12 and 13. Note that
there was no graphite exfoliation observed in this case studied
under the charge/discharge current density of 0.14 mA/cm.sup.2.
[0092] In Example 9, involving synthesis of ethyl
methoxyethoxyethyl sulfone (EMEES), 40 g NaOH was dissolved in 40 g
H.sub.2O and cooled with ice water. 62 g ethanethiol was added to
the solution slowly. The solution was stirred for a half hour
before 138.5 g chloroethyl methoxyethyl ether
(ClCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) was added. After
addition the solution was stirred at room temperature for several
hours before it was heated to reflux for overnight. The reaction
was stopped and cooled to room temperature. Ethyl
methoxyethoxyethyl sulfide
(CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) in
the upper organic layer was separated with a yield of 96%. The
resulting compound was oxidized with H.sub.2O.sub.2 and acetic
acid, as described in Example 1, to yield ethyl methoxyethoxyethyl
sulfone (EMEES).
[0093] In Example 10, involving characterization of ethyl
methoxyethoxyethyl sulfone (EMEES), the T.sub.g of EMEES is
-87.6.degree. C. as shown in Table 1. Salt solutions of EMEES were
prepared, as described in Example 3, and their ionic conductivities
were measured using the method described in Example 3. The
temperature dependence curve for EMEES containing 1.0M LiTFSI is
shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMEES are
shown in Table 2. The cyclic voltammogram of 1M LiTFSI/EMEES
electrolyte was measured, as described in Example 5, which is shown
in FIG. 4b.
[0094] In Example 11, involving synthesis of ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES), 40 g NaOH was dissolved
in 40 g H.sub.2O and cooled with ice water, 62 g ethanethiol was
added to the solution slowly. The solution was stirred for half
hour before 182.5 g chloroethyl methoxyethoxyethyl ether
(ClCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) was
added. After addition the solution was stirred at room temperature
for several hours before it was heated to reflux for overnight. The
reaction was stopped and cooled to room temperature. Ethyl
methoxyethoxyethoxyethyl sulfide
(CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.s-
ub.3) in the upper organic layer was separated with a yield of 95%.
The sulfide was further oxidized with H.sub.2O.sub.2 and acetic
acid, as described in Example 1, to obtain the ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES).
[0095] In Example 12, involving characterization of ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES), the T.sub.g of EMEEES
was -82.5.degree. C., as shown in Table 1. Salt solutions of EMEEES
were prepared, as described in Example 3, and their ionic
conductivities were measured using the method described in Example
3. The temperature dependence curve for EMEEES containing 1.0M
LiTFSI is shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMEEES are
shown in Table 2.
[0096] In Example 13, involving synthesis of dimethoxyethyl sulfone
(DMES), 50 ml 2-chloroethyl methyl ether, 70 g Na.sub.2S.9H.sub.2O,
17.6 g tetrabutylammonium bromide and 50 ml H.sub.2O were mixed
into a three-neck flask equipped with magnetic stirrer and reflux
condenser, and heated at 70.degree. C. with vigorous stirring. The
reaction was continued for overnight. The organic layer was
separated and dissolved in chloroform, washed with distilled water
several times to remove the ammonium salt and dried over anhydrous
sodium sulfate. Solvent was removed using a rotary evaporator, and
dimethoxyethyl sulfide was obtained with a yield of 63%. The
sulfide was oxidized with H.sub.2O.sub.2 and acetic acid, as
described in Example 1, to obtain the corresponding sulfone,
dimethoxyethylsulfone (DMES).
[0097] In Example 14, involving characterization of dimethoxyethyl
sulfone (DMES), the T.sub.g and T.sub.m of DMES are -90.7.degree.
C. and 47.0.degree. C., respectively, as shown in Table 1. Salt
solutions of DMES were prepared, as described in Example 3, and
their ionic conductivities were measured using the method described
in Example 3. The temperature dependence curve for DMES containing
1.0M LiTFSI is shown in FIG. 3. The T.sub.g and room temperature
ionic conductivities of 1.0M of different lithium salts in DMES are
shown in Table 2.
[0098] Implementations of features described in this specification
can be used to provide high oxidation resistance and high
conductivity. This combination of high oxidation resistance and
high conductivity can be used to provide, among other things,
burn-resistant, combustion-resistant electrolytic cells. Moreover,
great attention has recently been given to the difficulty of
producing highly conductive, flame retardant methods and devices
for electric current generation. When a sulfone as described in
this specification is utilized as a solvent to dissolve inorganic
electrolyte salts of highly oxidation resistant anions such as
ClO.sub.4, CF.sub.3SO.sub.3 (triflate), and in particular,
bis(trifluoromethane sulfonyl)imide(--N(CF.sub.3SO.sub.2).sub.2,
lithium imide), solutions can be obtained to provide both high
oxidation resistance and high ambient temperature conductivity.
This resistance to oxidation inhibits energy producing chemical
reactions such as those that might cause explosion or flame. The
result of this inhibition is the increased stability which can be
important in high energy or high temperature batteries.
[0099] While this specification contains many specifics, these
should not be construed as limitations on the scope of an invention
that is claimed or of what may be claimed, but rather as
descriptions of features specific to particular embodiments.
Certain features that are described in this specification in the
context of separate embodiments can also be implemented in
combination in a single embodiment. Conversely, various features
that are described in the context of a single embodiment can also
be implemented in multiple embodiments separately or in any
suitable sub-combination. Moreover, although features may be
described above as acting in certain combinations and even
initially claimed as such, one or more features from a claimed
combination can in some cases be excised from the combination, and
the claimed combination may be directed to a sub-combination or a
variation of a sub-combination. Similarly, while operations are
depicted in the drawings in a particular order, this should not be
understood as requiring that such operations be performed in the
particular order shown or in sequential order, or that all
illustrated operations be performed, to achieve desirable
results.
[0100] Only a few examples and implementations are disclosed.
Variations, modifications and enhancements to the described
examples and implementations and other implementations may be made
based on what is disclosed.
* * * * *