NONAQUEOUS ELECTROLYTE FOR ELECTROCHEMICAL ENERGY STORAGE DEVICE AND ELECTROCHEMICAL ENERGY STORAGE DEVICE MAKING USE OF THE SAME

摘要

A nonaqueous electrolyte solution for electrochemical energy-storing device, comprising (a) a lithium salt, (b) a quaternary ammonium salt containing a quaternary ammonium cation having three or more methyl groups, and (c) a nonaqueous solvent, that allows reliable insertion and extraction of lithium ions into and out of a negative-electrode material having a graphite structure even when the quaternary ammonium salt is dissolved in the nonaqueous electrolyte solution, provides an electrochemical energy-storing device that allows a higher voltage setting in charge and is resistant to capacity deterioration even after repeated charge/discharge cycles.