| 摘要 |
PROBLEM TO BE SOLVED: To provide excellent initial and post-preservation high-rate discharging characteristics and to improve cycle characteristics by using a mixed solvent of cyclic carbonic acid ester and noncyclic carbonic ester as the solvent of an electrolyte. SOLUTION: A mixed solvent of cyclic carbonic acid ester and noncyclic carbonic acid ester is used as the solvent of a nonaqueous electrolyte. Ethylene carbonate, propylene carbonate, 1,2-butylene carbonate or vinylene carbonate is used as the cyclic carbonic acid ester, for example. Dimethyl carbonate, diethyl carbonate or methyl ethyl carbonate is preferably used as the noncyclic carbonic acid ester. One kind may be singularly used or two or more kinds may be used together for the cyclic carbonic acid ester and noncyclic carbonic acid ester. Lithium hexafluoride is most suitably used as the solute of the nonaqueous electrolyte. The cyclic carbonic acid ester reacts with a negative electrode active material to form a film excellent in ionic conductivity on the surface of a negative electrode, and the elution of the active material is prevented. |
