NONAQUEOUS ELECTROLYTE AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY HAVING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an electrochemically stable electrolyte having superior charge and discharge cycle characteristics, by enhancing the working voltage of a nonaqueous electrolyte secondary battery so as to be used with a high voltage of 4.4 V or more.SOLUTION: A solid electrolyte boundary surface is formed at least in the positive electrode, by adding 0.1-2.0 wt% of a fluorination cyclic ester compound, represented byα,α-difluoro-β-dimethyl-β-butyrolactone to a nonaqueous electrolyte. As a result, even when having an average discharge potential of 4.4 V or more, decomposition of nonaqueous electrolyte is suppressed, and the cycle characteristics of a nonaqueous electrolyte secondary battery are improved.