Nonaqueous electrolyte battery

Details Nonaqueous electrolyte battery Nonaqueous electrolyte battery

1999-01-27

2001-04-24

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S311000, C429S322000, C429S323000, C429S324000

Reexamination Certificate

active

06221533

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an improvement in the storage property of a nonaqueous battery which uses lithium as an active material.
BACKGROUND OF THE INVENTION
Lithium primary and secondary batteries which use lithium as the negative electrode active material have lately attracted attention as high energy density batteries, and much active research is being conducted.
As a solvent of the nonaqueous electrolyte for these types of batteries, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, sulfolane, dimethoxy ethane, tetrahydrofuran and dioxolane and the like can be used alone or in the form of a mixture of two or more of these substances. As a solute dissolved in the solvent there can be mentioned LiPF
6
, LiBF
4
, LiClO
4
, LiCF
3
SO
3
, LiAsF
6
, LiN(CF
3
SO
2
)
2
, LiCF
3
(CF
2
)
3
SO
3
or the like.
It is known that a nonaqueous electrolyte including dioxolane as a solvent improves battery properties (Japanese patent publication (Laid-Open) Sho 60-91565). However, there is a problem when dioxolane is used as solvent that a negative electrode in which lithium is an active material reacts chemically with the dioxolane, and reduces battery capacity after storage.
It is commercially important for this kind of battery to inhibit self-discharge during storage.
OBJECT OF THE INVENTION
An object of the present invention is to reduce self-discharge during storage of a nonaqueous electrolyte battery and to provide a nonaqueous electrolyte which increases storage properties.
SUMMARY OF THE INVENTION
The present invention provides a nonaqueous electrolyte lithium primary or secondary battery having a positive electrode, a negative electrode comprising lithium, lithium alloy or a material capable of occluding and discharging lithium, a nonaqueous electrolyte including an organic solvent containing dioxolane or a derivative thereof in an amount of not less than 10.0 wt %, wherein the nonaqueous electrolyte includes LiN(C
m
F
2m+1
SO
2
)(C
2
F
2n+1
SO
2
) (1) (where m is a natural number of 1 or greater, and n is a natural number of 2 or greater) as an electrolytic solute. 4-Methyldioxolane and 2-methyldioxolane are illustrated as derivatives of dioxolane.
When the negative electrode is lithium metal, a remarkable improvement can be expected.
It is preferable to contain 0.1~2.0 mol of the electrolytic solute per 1 l of the nonaqueous electrolyte.
A preferable electrolyte can be provided when m is 1 or 2, and n is 2, 3 or 4 in formula (1). Concretely speaking, when m is 1, and n is 2, 3 or 4 in the formula (1), the electrolytic solute is LiN(CF
3
SO
2
)(C
2
F
5
SO
2
), LiN(CF
3
SO
2
) (C
3
F
7
SO
2
) or LiN(CF
3
SO
2
)(C
4
F
9
SO
2
), respectively, and when m is 2, and n is 2, 3 or 4 in formula (1), the electrolytic solute is LiN(C
2
F
5
SO
2
)
2
, LiN(C
2
F
5
SO
2
)(C
3
F
7
SO
2
) or LiN(C
2
F
5
SO
2
)C
4
F
9
SO
2
), respectively.
It is preferable to include a nitrogen-containing compound other than the compound of formula (1) in the nonaqueous electrolyte. 0.01~10.0 wt % of the nitrogen-containing compound in the nonaqueous electrolyte is most preferable. Cyclic nitrogen-containing compounds are preferred and 3,5-dimethylisooxazole and pyridine are illustrated as concrete examples of the nitrogen-containing compounds.
As the other solvent comprising the electrolyte, there can be used ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, sulfolane, 3-methyl sulfolane, dimethoxy ethane, tetrahydrofuran, 2-methyl tetrahydrofuran alone or as a mixture of two or more of these. The solvent, of course, is not limited to these.
As the positive electrode for this battery, there can be used a metallic oxide containing of at least one metal selected from the group consisting of manganese, cobalt, nickel, vanadium and niobium. However, the positive electrode is not so limited.
The negative electrode for this battery is lithium, a lithium alloy or a material capable of occluding and discharging lithium, for example, lithium-aluminum alloy, carbon material (for example, coke or graphite) and the like.
If a nonaqueous electrolyte containing 10.0 wt % or more of dioxolane as a solvent of a solvent mixture contains a specific electrolytic solute represented by LiN(C
m
F
2m+1
SO
2
)(C
n
F
2n+1
SO
2
) (1) (where m is a natural number of 1 or greater, and n is a natural number of 2 or greater), reaction between lithium and the nonaqueous electrolyte can be inhibited. As the result, decomposition of the nonelectrolyte can be inhibited. A storage property of this kind of the nonaqueous electrolyte battery can be improved.


REFERENCES:
patent: 5783333 (1998-07-01), Mayer
patent: 6007947 (1998-07-01), Mayer
patent: 197 57 126 (1999-06-01), None
patent: 11214016 (1999-08-01), None
Wang, X. et al.; “Lithium Imide Electrolytes with Two-Oxygen-Atom-Containing Cycloalkane Solvents for Lithium Metal Rechargeable Batteries”; Journal of the Electrochemical Society, 147(7), 2421-2426, (2000).*
Arai, J. and Peter, L.; “Anodic Dissolution of Aluminum in Organic Electrolytes Containing Perfluoroalkylsulfonyl Imides”; Journal of Applied Electrochemistry, 29; 1053-1061, 1999.

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