| 摘要 |
PROBLEM TO BE SOLVED: To restrain increase of internal resistance during long term storage at a room temperature after a partial discharge by adding a specific organic compound to nonaqueous electrolyte. SOLUTION: Compound added to nonaqueous electrolyte is represented by a formula. In the formula, R1, R2, and R3 are hydrocarbon groups or carbon cyclic compound containing 1-4 carbons. For restraining added amount in the electrolyte and preventing excessive dilution of the electrolyte, compound with relatively low molecular weight is preferably used. R1 and R3 in the formula are preferably methyl groups, ethyl groups, or n-butyl groups. As especially preferable compound, methyl acetoacetate is used. Existence of this compound at 500-5000 ppm concentration in nonaqueous electrolyte is effective. Thus, decomposition of a low-boiling point solvent by a catalyst reaction of manganese dioxide or the like is prevented, and a discharge characteristic of a battery can be kept for one or more years. |
