Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
1998-09-11
2001-10-02
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S315000, C429S317000, C429S322000, C429S330000, C252S062200
Reexamination Certificate
active
06296973
ABSTRACT:
FIELD OF INVENTION
The invention concerns new polar solvents and new electrolytic compositions comprising the same, and having a large range of stability, as required for applications in the field of electrochemistry.
BACKGROUND OF THE INVENTION
Polar aprotic solvents such as cyclic or linear carbonates, or ethers used alone or in mixtures, are known in various electrolytic compositions. The stability of these products towards highly negative potentials, close to those of alkaline metals, or highly positive (≧4V with respect to Li
+
/Li°), are not satisfactory, and lithium batteries containing electrolytes obtained from the dissolution of a lithium salt in these solvents create serious safety problems. Products of the amide type, whether linear or cyclic, such as dimethylformamide or N-methylpyrrolidinone, possess excellent properties as solvents, but are oxidized at potentials that are still lower, in the order of 3.7 V with respect to Li
+
/Li°.
Numerous materials of positive electrodes, such as mixed oxides of transition metals and lithium work under potentials near 4 V with respect to Li
+
/Li° and therefore require electrolyte stabilities significantly higher than that value. For example, products like Li
1−y
Co
1−x−z
Ni
x
Al
y
O
2
wherein x+y≦1 and z≦0,3); manganese spinels Li
1−&agr;
Mn
2−x
M
x
O
4
.Li
1−&agr;
Co
1−x−y
Ni
x
Al
y
wherein 0≦x+y≦1; 0≦y≦0,3; 0≦&agr;≦1 and M=Li, Mg, Al, Cr, Ni, Co, Cu, Ni, Fe.
U.S. Pat. Nos. 4,851,307 and 5,063,124 describe electrolytes comprising a salt, a solvating polymer and an aprotic sulfamide of the general formula
R
1
R
2
NSO
2
R
3
R
4
wherein R
1
, R
2
, R
3
and R
4
, the same or different, are independently selected from C
1-10
alkyl or C
1-10
oxaalkyl. An example of the product of that group is the tetraethylfulfamide (R
1
═R
2
═R
3
═R
4
═C
2
H
5
). These materials have increased stability towards reducing or basic agents present and having potentials near those of alkaline metals. However, they are oxidized at potentials between 3.8 and 4V with respect to Li
+
/Li°.
EP 0 339 284 discloses dielectric and insulating compounds like perfluoro-acylamides or perfluoro-sulfonamides R
F
CONA
1
A
2
and R
F
SO
2
NA
1
A
2
, wherein A
1
and A
2
are alkyl groups. The proposed use of these products in capacitors implies that the materials are not conductive and that the impurities and inevitable contaminants, particularly ionic products, are not inducing significant conductivity.
The publication of Sartori et al. in an abstract of a meeting of the Electrochemical Society, Volume 97-1, May 1997, describes certain sulfonamides that could be used as electrolytes in a battery or in an energy storage system.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided novel polar solvents and novel electrolytic compositions comprising the same and having a high degree of stability, as required for applications in the field of electrochemistry. More specifically, the solvents of the present invention are of the general formula
R
1
R
2
NX(Z)R
7
wherein
X═C or SO;
Z═O, NSO
2
NR
3
R
4
or NCN;
R
1
R
2
are the same or different and are C
1-18
alkyl, C
1-18
oxaalkyl, C
1-18
alkylene or C
1-18
oxaalkylene;
R
3
to R
6
are the same or different and are C
1-18
alkyl or C
1-18
oxaalkyl;
R
7
is R
F
, R
F
CH
2
O—, (R
F
)
2
CHO—, (R
F
CH
2
)
2
N— or NR
5
R
6
;
R
F
is fluorine, C
1-4
alkyl, C
1-4
oxaalkyl or C
1-4
azaalkyl wherein the alkyl chain is preferably essentially fluorinated and partly chlorinated,
with the provisos that:
1) if Z═O, then R
F
is not C
1-4
alkyl; and
2) if Z═O and X═SO, then R
5
or R
6
is not C
1-4
alkyl or C
1-4
oxaalkyl.
The expression “essentially fluorinated” means that the degree of fluorination in the chain is sufficient to provide properties similar to those obtained with a chain entirely perfluorated, such as a hydrophobic character and properties of attracting electrons. Preferably, at least half of the hydrogen atoms of the chain are replaced by fluorine atoms. The expression “partially chlorinated” means that within the essentially fluorinated products, the hydrogen atoms remaining are at least partially replaced with chlorine atoms.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, materials with a highly polar amide function are used for preparing electrolytic compositions useful for electrochemical applications. It has unexpectedly been found that groups strongly attracting electrons, when combined with the amide function, allow the maintenance of solubilizing power towards ionic products, particularly those having a highly delocalized anionic charge, and thus inducing high ionic conductivities. By adding a polar polymer to these compositions, there is obtained electrolytes with mechanical properties allowing the fabrication of films for use in electrochemical devices, and increasing the security when in operation. Depending on the amount of polar solvent and polymer in the electrolytic compositions, the consistency thereof can be adjusted to a gel or a plasticized polymer. Further, the polymers can be reticulated to improve mechanical properties.
The electrolytic compositions of the present invention have higher stability when compared to materials of the prior art, particularly at very anodic potentials, especially those exceeding 4 V with respect to Li
+
/Li°.
Preferred low energy reticular salts that are soluble in the polar solvents of the present invention to form conductive solutions comprise those having a delocalized charge, such as I
−
, ClO
4
−
, BF
4
−
, PF
6
−
, AsF
6
−
, SbF
6
−
, R
F
SO
3
−
, XSO
2
NSO
2
X′
−
, (XSO
2
)(X′SO
2
)(Y)C
−
and mixtures thereof, wherein
X and X′ is R
F
, R
F
CH
2
O—, (R
F
)
2
CHO—, (R
F
CH
2
)
2
N—, R
8
, R
9
R
10
N—, with the proviso that at least one X or X′ is R
F
, R
F
CH
2
O—, (R
F
)
2
CHO—, (R
F
CH
2
)
2
N—;
Y═R
F
, R
F
SO
2
or CN;
R
F
is as defined above; and
R
8
to R
10
are the same or different, and are C
1-18
alkyl or —C
1-18
oxaalkyl.
R
F
and R
8
-R
10
can be part of a molecular chain. Also preferred are anions derived from 4,5-dicyano-1,2,3-triazole, 3,5-bis(R
F
)-1,2,4-triazole, tricyanomethane, pentacyanocyclopentadiene and pentakis(trifluoromethyl)cyclopentadiene and anions derived from cyanamide and malononitrile, i.e., R
F
SO
2
NCN
−
, C(CN)
3
−
, R
F
SO
2
C(CN)
2
−
. Preferred cations comprise those derived from alkaline metals, more preferably lithium, alkaline earth metals, and organic cations of the “onium” type, such as ammonium, imidazolium, sulphonium, phosphonium and oxonium.
With respect to the electrolytic compositions of the present invention, they include those containing at least one polar solvent as defined above in combination with one or more polar molecules acting as a co-solvent. Such other polar molecules include solvents capable of forming compatible mixtures, such as dialkyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycols preferably having a mass of from 400 to 2000; or esters, preferably carbonic acid esters, whether linear or cyclic, such as dimethylcarbonate, methylethylcarbonate, diethylcarbonate, ethylene carbonate, propylene carbonate, or esters such as &ggr;-butyrolactone, nitrites such as glutaronitrile, or 1,2,6-tricyanohexane. These other polar molecules, or co-solvent, can be added alone or in mixtures to the solvent of the present invention. An example of the preferred mixture is ethylene carbonate with a dialkyl ether.
The present invention further includes solid electrolytes obtained by the addition of the polymer to a solvent or solvent-co-solvent mixture containing at least one salt as defined above in solution. The amount of polymer can be selected so that the solvent acts as a plasticizing agent of the polymer, i.e. in concentration of 3 to 30% by weight, preferably
Armand Michel
Baril Daniel
Bergeron Jean-Yves
Brouillette Dany
Michot Christophe
Hydro - Quebec
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Weiner Laura
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