Sulfonylimide compounds

Details Sulfonylimide compounds Sulfonylimide compounds

1998-08-25

2002-02-26

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S314000, C429S316000, C429S317000, C540S468000, C549S011000, C564S102000, C568S030000, C568S036000

Reexamination Certificate

active

06350545

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to sulfonylimide conductive salts having mixed fluorocarbon and hydrocarbon groups or having all hydrocarbon groups, and the use thereof in electrolytes for electrochemical cells, such as lithium batteries.
BACKGROUND
Industry is continually searching for novel compounds which can provide ionic conductivity when dissolved or dispersed in other materials. These compounds often find use, for example, as conductivity additives or enhancers, as cationic polymerization initiators or catalysts, as anti-static additives, as electrochemical sensors, and as surfactants. Such compounds are especially useful when employed in combination with other materials to form electrolytes to conduct electrical charge, for example, when used in electrochemical cells and devices such as batteries, fuel cells, electrochromic devices, capacitors, and supercapacitors.
With respect to the specific application of electrolyte compounds in electrochemical cells and devices, there is both a current and projected future demand for high energy density, lightweight, rechargeable power sources for use in automotive, industrial and consumer markets. Many of these needs can be met by lithium-ion battery technology, which requires the use of electrolytic salts dissolved in a non-aqueous solvent or polymer to act as an electrolyte. This electrolyte solution acts as the medium through which ionic conduction can occur between electrodes, providing charge balance within an electrochemical cell such as a battery.
Of course, new electrolytic compounds must exhibit specific chemical and physical properties to be useful in electrochemical cells and devices. Of primary importance, the compounds must exhibit good ionic conductivity and should be thermally and electrochemically stable. Additionally, the compounds must also exhibit good solubility at high concentration in common electrolyte solvents and/or polymers; they should exhibit inertness to other battery components (e.g., not cause corrosion of electrodes or current collectors); they should be relatively non-toxic; they should have acceptable environmental impact, and preferably they should be able to be produced at an economically feasible price. In the case of secondary (i.e., rechargeable) batteries, the compounds should exhibit good cycling behavior at room temperature and elevated temperature and should produce electrochemical cells that can be operated and maintained with minimal concerns for safety (e.g., explosions caused by thermal runaway).
There are currently only a small number electrolytic compounds known to be suitable for use in lithium-ion batteries; all are lithium salts and all have identifiable drawbacks. The most common electrolyte compound is LiPF
6
, which exhibits good conductivity and corrosion resistance, but is thermally and hydrolytically unstable, decomposing to liberate fluoride ion which is detrimental to cell performance. Other compounds having potential uses in lithium electrolytes include LiAsF
6
(toxic), LiBF
4
(relatively poor conductivity, thermally and hydrolytically unstable), and LiClO
4
(thermally unstable, potentially explosive). There are also a number of known organofluorine lithium compounds, but each of these has its own individual shortcomings. Molecules like LiOSO
2
CF
3
and LiN(SO
2
CF
3
)
2
are thermally very stable but can be corrosive to aluminum current collectors at the operative voltage of a lithium ion cell, and LiC(SO
2
CF
3
)
3
is very expensive to prepare.
There is a continuing need for new electrolyte compounds which can perform at useful conductivity levels, and that are easily handled and produced at a reasonable cost.
SUMMARY OF THE INVENTION
Conductive ionic compounds have been discovered that are lower cost alternatives to the relatively expensive perfluorinated sulfonates, sulfonylimides and sulfonylmethides now commercially used in electrochemical cells such as lithium batteries, fuel cells, capacitors, supercapacitors and electrochromic windows. These ionic compounds are analogous to perfluoroalkanesulfonylimide compounds in which some or all of the perfluoroalkyl groups have been replaced with oxygen or nitrogen heteroatoms attached to fluorine-free organic groups. By having part or even all of the expensive perfluoroalkyl groups replaced, the compounds of this invention can be made at a lower cost per pound and, having lower molecular weights, can be used at lower weight concentrations in electrolytes to produce a given molarity solution. Nonetheless, these relatively inexpensive compounds exhibit good conductivity and low corrosivity.
The present invention includes sulfonylimide compounds which are particularly useful as conductive salts in battery electrolytes.
In one aspect, the present invention includes novel salts of the Formula I:
N
−
(SO
2
XR
p
)
m
(SO
2
R′)
o
1
M
n+
wherein:
m is 1 or 2and m+o is 2;
X is independently O or N;
p is 1 when X is O, and p is 2 when X is N;
R is each independently a monovalent hydrocarbon group; two R groups when taken together form a divalent hydrocarbon group, e.g. an alkylene group or a 1,2-phenylene group, joined to two X atoms, in which the hydrocarbon groups are uninterrupted or interrupted by a heteroatom; or two R groups when taken together may form a three- to six-membered ring with a nitrogen atom, which ring may be further interrupted by a heteroatom;
R′ is a hydrocarbon group or a straight or branched acyclic fluoroalkyl group having from 1 to 12 carbon atoms, a cyclic fluoroalkyl group having from 3 to 12 carbon atoms, or a fluorocycloalkyl-fluoroalkyl group where the fluoroalkyl group has from 1 to 4 carbon atoms, in which the fluoroalkyl and fluorocycloalkyl groups are uninterrupted or interrupted by a heteroatom; or an R group and an R′ group when taken together may form a ring, which ring may be further interrupted by a heteroatom; and
M
n+
is a cation having a valence of n;
with the proviso that when m is 2, M
n+
is a metal or alkylammonium cation of the formula R″
4
N
+
, where R″ is independently alkyl having 1 to 4 carbon atoms.
A second aspect of the present invention includes an electrolyte for use in electrochemical cells containing:
(a) a salt of the Formula I,
N
−
(SO
2
XR
p
)
m
(SO
2
R′)
o
1
M
n+
wherein:
m is 1 or 2and m+o is 2;
X is independently O or N;
p is 1 when X is O, and p is 2 when X is N;
R is each independently a monovalent hydrocarbon group; two R groups when taken together form a divalent hydrocarbon group, e.g. an alkylene group or a 1,2-phenylene group, joined to two X atoms, in which the hydrocarbon groups are uninterrupted or interrupted by a heteroatom; or two R groups when taken together may form a three- to six-membered ring with a nitrogen atom, which ring may be further interrupted by a heteroatom;
R′ is a hydrocarbon group or a straight or branched acyclic fluoroalkyl group having from 1 to 12 carbon atoms, a cyclic fluoroalkyl group having from 3 to 12 carbon atoms, or a fluorocycloalkyl-fluoroalkyl group where the fluoroalkyl group has from 1 to 4 carbon atoms, in which the fluoroalkyl and fluorocycloalkyl groups are uninterrupted or interrupted by a heteroatom; or an R group and an R′ group when taken together may form a ring, which ring may be further interrupted by a heteroatom; and
M
n+
is a cation having a valence of n; and
(b) a matrix material.
A third aspect of the present invention includes a battery having at least one cathode, at least one anode and an electrolyte as defined above.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this application the following definitions apply:
“Battery” includes all electrical energy storage devices, including capacitors, electrochromic devices, and electrochemical cells.
“Macromolecular material” refers to a homopolymer, copolymer, or combination thereof, which may or may not be cross-linked and/or plasticized.
“Gel” refers to a macromolecular material swollen with a liquid.
“Matrix” or “matrix material” refe

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