Cyano-substituted methide and amide salts

Details Cyano-substituted methide and amide salts Cyano-substituted methide and amide salts

1998-08-25

2001-09-25

Acquah, Samuel A. (Department: 1711)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C558S437000, C558S439000, C534S735000, C568S031000, C429S122000, C429S128000, C429S232000

Reexamination Certificate

active

06294289

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to cyano-substituted salts including cyano-substituted methides and amides.
BACKGROUND OF THE INVENTION
Industry is continually searching for new weakly coordinating anions which form highly dissociating salts. Such salts can often be useful as conductivity additives or enhancers, when dissolved or dispensed in other materials; as cationic polymerization initiators or catalysts; as anti-static additives; as surfactants; and often, in combination with other materials, can be used to conduct electrical charge, for example, as electrolytes (ionic conductors) within electrochemical cells such as batteries, fuel cells, capacitors, supercapacitors and electrochemical sensors, etc.
Of course these salts should exhibit specific chemical and physical properties to be useful in such applications. First of all they must exhibit good ionic conductivity. In many applications they must also exhibit thermal and electrochemical stability. They should not cause damage to other components of systems in which they are used (e.g., corrosion). They should have acceptable environmental impact; and, they preferably can be produced at an economically feasible price. When employed in electrochemical cells the salts should exhibit good cycling properties and should produce electrochemical cells that can be operated and maintained with minimal concerns for safety.
With respect to the very specific application of salt compounds in electrochemical cells, 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 potentially be met by lithium-ion battery technology, which requires the use of electrolyte salts dissolved in a non-aqueous solvent to act as an electrolyte. This electrolyte solution acts as the medium in which ionic conduction can occur between electrodes, providing charge balance within an electrochemical cell, such as a battery.
There are currently only a small number of electrolyte salts known to be suitable for use in lithium-ion batteries, and all have identifiable drawbacks. The most common electrolyte salt is LiPF
6
, which exhibits good conductivity and corrosion resistance, but is thermally and hydrolytically unstable. Hydrolytically unstable means that exposure to water will cause decomposition to form fluoride ions. Other salts having potential uses as lithium electrolytes include LiAsF
6
(toxic), LiBF
4
(relatively poor conductivity), and LiClO
4
(potentially explosive). There are also a number of known organofluorine lithium salts, but each of these has its own individual short-comings. 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, and LiC(SO
2
CF
3
)
3
is expensive to produce for most commercial scale applications.
The battery industry is currently seeking electrolyte salts which can perform at useful conductivity levels, and that are easily handled and can be produced at a reasonable cost.
SUMMARY OF THE INVENTION
Amide and methide salts, including in the case of an amide salt one cyano (—CN) group, and in the case of a methide salt, two cyano groups, have been found useful in applications requiring a high degree of ionic dissociation. The salts are especially useful as electrolyte components in electrochemical cells such as batteries, fuel cells, capacitors, supercapacitors, electrochemical sensors and electrolytic cells, by providing a means for ionic conduction and transport.
Accordingly, the present invention relates to an electrolyte which includes a salt of an N-cyano-substituted amide, (e.g., an N-cyano-substituted carboxamide, or an N-cyano-substituted sulfonamide), a dicyano-substituted sulfonyl methide, a dicyanoacyl methide, or a mixture thereof in a matrix material.
More specifically, the present invention includes as an electrolyte a matrix material and a salt of the formula
 R—[Q—X
−
(CN)
n
]
y
y/mM
m+
  (I)
wherein y is 1 or 2;
X is C or N, which when X is C, n is 2 and when X is N, n is 1;
R is a fluorine atom, a hydrocarbon or a fluorinated hydrocarbon group;
Q is a linking group; and
M
m+
is a cation having a valence of m. A mixture of salts of formula I may also be included in the electrolyte.
Another aspect of the present invention is an electrochemical cell containing the above described electrolyte, an anode and a cathode.
A further aspect of the present invention includes certain novel methide and amide salts which are salts of an N-cyano-substituted amide, (e.g., an N-cyano-substituted carboxamide or an N-cyano-substituted sulfonamide), a dicyano-substituted sulfonyl methide, or a dicyanoacyl methide.
More specifically, novel salts of the invention include methide salts of the formula
R—[SO
2
—C
−
(CN)
2
]
y
y/mM
m+
  (II)
wherein y is 1 or 2;
R is a fluorine atom or a perfluorinated hydrocarbon group; and
M
m+
is a cation having a valence of m.
Novel salts of the invention also include amide salts of the formula
R—[Q—N
−
CN]
y
y/mM
m+
  (III)
wherein y is 1 or 2;
R is a fluorine atom or a perfluorinated hydrocarbon group;
Q is a linking group; and
M
m+
is a cation having a valence of m.
Further salts include salts containing polymerizable groups, for example, methide salts of the formula
 R—[Q—C
−
(CN)
2
]
y
y/mM
m+
  (IV)
wherein y is 1 or 2;
R is a halogenated or non-halogenated polymerizable group;
Q is a linking group; and
M
m+
is a cation having a valence of m; and amide salts of the formula
R—[SO
2
—N
−
CN]
y
y/mM
m+
  (V)
wherein y is 1 or 2;
R is a halogenated or non-halogenated polymerizable group; and
M
m+
is a cation having a valence of m.
DETAILED DESCRIPTION
Definitions
Throughout this application the following definitions apply:
“Electrochemical cell” includes all electrical energy storage devices and electrolytic cells, including capacitors, supercapacitors, electrochromic devices, electrochemical sensors, fuel cells and batteries.
“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 physically or chemically cross-linked polymer swollen with solvent.
“Matrix” or “matrix material” refers to a medium (e.g., a solid, liquid, gel or plasticized polymer) in which electrolyte salts may be dissolved or dispersed to form an ionically conductive electrolyte. For a “lithium ion battery,” the matrix is liquid; for a “lithium polymer battery,” the matrix is a solid, gel or plasticized polymer.
“Plasticized polymer” refers to a polymer containing a low molecular weight additive, such as an organic solvent.
Voltages specified refer to electrical potential differences between a positive electrode measured relative to a Li/Li
+
reference electrode, except where otherwise noted.
A fluorocarbon group may be either a partially or fully fluorinated (i.e., perfluorinated) hydrocarbon chain. A partially fluorinated hydrocarbon chain exists where only a portion of the hydrogen atoms in the hydrocarbon has been replaced by fluorine atoms. In a fully fluorinated or perfluorinated hydrocarbon chain, essentially all of the hydrogen atoms, e.g. at least 90%, attached to carbon have been replaced by fluorine. Thus, the non-skeletal valence bonds are preferably carbon-to-fluorine bonds. However, an occasional carbon bonded hydrogen atom, bromine atom or chlorine atom may be present in a fully fluorinated hydrocarbon chain.
A “hydrocarbon group” refers to a monovalent or divalent straight or branched aliphatic group, a cycloaliphatic group, a cycloaliphatic-aliphatic group, or an aryl, biaryl or aralkyl group. These groups are further defined below.
“A straight or branched aliphatic group” refers to a hydrocarbon radical, e.g. an alkyl group, which is either in the form of a straight or branched ch

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