| abstract |
The purpose of the present invention is to provide: a nonaqueous electrolyte solution for secondary batteries, which has excellent rate characteristics, excellent initial charge/discharge characteristics, excellent cycle characteristics, low reactivity between the positive electrode and the negative electrode and sufficient conductivity, and which makes a secondary battery less susceptible to thermal runaway; and a lithium ion secondary battery which uses the nonaqueous electrolyte solution for secondary batteries.nA nonaqueous electrolyte solution for secondary batteries, which is composed of a lithium salt (the total number of moles of lithium atoms: N Li ) and a liquid composition, and wherein the liquid composition contains a specific fluorine-containing solvent (α) and a cyclic carboxylic acid ester compound (the total number of moles: N A ), and optionally contains a specific compound (β) (the total number of moles: N B ). The content of the fluorine-containing solvent (α) is 40-80% by mass; N A /N Li is 1.5-7.0; and (N A + N B )/N Li is 3-7.0. A lithium ion secondary battery which uses this nonaqueous electrolyte solution for secondary batteries. |