NONAQUEOUS ELECTROLYTE, CAPACITOR DEVICE USING SAME, AND CARBOXYLIC ACID ESTER COMPOUND USED IN SAME

The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I). In the formula, each of Rand Rindependently represents a hydrogen atom, a —C(═O)—ORgroup, or the like, and Rand Rmay be bonded to each other to form a ring structure. Rrepresents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and Rrepresent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O)— group, an —S(═O)—R—S(═O)— group or a CRRgroup, Rrepresents an alkylene group having 1 to 4 carbon atoms, and each of Rand Rrepresents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.