Abstract: A subject for the invention is to provide an electrolyte solution and a secondary battery which are preventd from causing or suffering battery performance deterioration in high-temperature storage or high-temperature trickle charge. The invention relates to a nonaqueous electrolyte solution for a secondary battery which comprises solute, phosphinic ester compound, and nonaqueous organic solvent containing these, characterized in that the content of the phosphinic ester compound has been regulated to a specific amount based on the total weight of the nonaqueous electrolyte solution.

Abstract: A subject for the invention is to provide an electrolyte solution and a secondary battery which are prevented from causing or suffering battery performance deterioration in high-temperature storage or high-temperature trickle charge. The invention relates to a nonaqueous electrolyte solution for a secondary battery which comprises solute, phosphinic ester compound, and nonaqueous organic solvent containing these, characterized in that the content of the phosphinic ester compound has been regulated to a specific amount based on the total weight of the nonaqueous electrolyte solution.

Abstract: In an electric double layer capacitor and electrolytic solution, decomposition of at least one of an open-chain carbonate and a cyclic carbonate can be controlled under high temperature conditions, initial performance and maintained ratio of capacitance are superior, and energy density is high, when graphitized alkali-activated carbon is used as an electrode material and at least one of an open-chain carbonate and a cyclic carbonate is used in an organic electrolytic solution. The electric double layer capacitor includes electrodes containing alkali-activated carbon including graphitized carbon material, and an organic electrolytic solution in which a supporting salt is dissolved in solvent including aromatic carboxylate and at least one of an open-chain carbonate and a cyclic carbonate, in which the content of the aromatic carboxylate is not more than 50 weight % relative to the total weight of the solvent.

Abstract: A nonaqueous electrolyte solution for secondary batteries which is an electrolyte solution for secondary batteries obtained by dissolving a lithium salt in a nonaqueous solvent, wherein the nonaqueous solvent is a solvent mainly comprising a lactone compound and the content of hydroxy carboxylic acids in the electrolyte solution is 1 mmol/kg or lower and a secondary battery employing the same are excellent in high-temperature storage characteristics, cycle characteristics, and capacity retention characteristics and in various cell characteristics in a wide temperature range and safety such as firing properties.

Abstract: A subject for the invention is to provide an electrolyte solution and a secondary battery which are prevented from causing or suffering battery performance deterioration in high-temperature storage or high-temperature trickle charge. The invention relates to a nonaqueous electrolyte solution for a secondary battery which comprises solute, phosphinic ester compound, and nonaqueous organic solvent containing these, characterized in that the content of the phosphinic ester compound has been regulated to a specific amount based on the total weight of the nonaqueous electrolyte solution.

Abstract: A nonaqueous electrolyte solution for secondary batteries which is an electrolyte solution for secondary batteries obtained by dissolving a lithium salt in a nonaqueous solvent, wherein the nonaqueous solvent is a solvent mainly comprising a lactone compound and the content of hydroxy carboxylic acids in the electrolyte solution is 1 mmol/kg or lower and a secondary battery employing the same are excellent in high-temperature storage characteristics, cycle characteristics, and capacity retention characteristics and in various cell characteristics in a wide temperature range and safety such as firing properties.