| 摘要 |
PROBLEM TO BE SOLVED: To improve a charging preserving characteristic by providing nonaqueous electrolyte by dissolving imide salt of lithium and/or a carbonate of lithium in a solvent containing halogenated ring cabonic ester. SOLUTION: A solvent preferably containing 20 volume % or more of halogenated ring carbonic ester by substituting one or more of hydrogens of R<1> , R<2> , R<3> and R<4> of ring carbon ester of a formula with fluorine, chorine or bromine, is used as nonaqueous electrolyte. Preferably, LiN(CnF2n+1 SO2 )2 and/or LiC(CmF2m+1 SO2 )2 is contained by 0.3 to 2.0 mole/l in this. (n and m are 1, 2, 3 or 4). Therefore, a coating film to restrain self-discharge is formed on an interface between a positive electrode, a negative electrode and the nonaqueous electrolyte, and also stably exists even in a charging condition. The ring carbonic ester of the formula may be substituted with chain carbonic ester of R<5> OCOOR<6> . (R<5> and R<6> are a methyl group of an ethyl group) [In the formula, R<1> , R<2> and R<3> are hydrogen, and R<4> is hydrogen, a methyl group or an ethyl group]. |
