| 摘要 |
PROBLEM TO BE SOLVED: To suppress the decomposition of an organic solvent on negative electrode side and improve the charge and discharge efficiency by using a fluorine-containing ester compound as a mixture with a nonaqueous electrolyte, and setting the reduction potential of the fluorine-containing ester compound to a specified value to the oxidation-reduction potential of lithium. SOLUTION: The reduction potential of a fluorine-containing ester compound is set to 1.0-0.7 to the oxidation-reduction potential (Li/Li+) of lithium. The fluorine-containing ester compound is represented by the general formula R<1> CFXCOOR<2> . In the formula, R<1> represents hydrogen atom, fluorine atom, or a 1-3C alkyl group, and R<2> represents a 1-2C alkyl group. More specifically, CHF2 COOCH3 , CHF2 COOC2 H5 , and CH3 CF2 COOCH3 are preferably used. As a carbonic ester organic solvent used together with the fluorine-containing ester compound as an electrolyte, propylene carbonate, ethylene carbonate or the like can be given. |
