METHOD FOR STABILIZING LIPF6, ELECTROLYTE SOLUTION FOR NONAQUEOUS SECONDARY BATTERIES HAVING EXCELLENT THERMAL STABILITY, AND NONAQUEOUS SECONDARY BATTERY HAVING EXCELLENT THERMAL STABILITY

摘要

[Problem] To provide: a method for stabilizing a solution that contains LiPF₆ by increasing thermal stability of LiPF₆ without changing the structure thereof; an electrolyte solution for nonaqueous secondary batteries, which has increased thermal stability; and a nonaqueous secondary battery which has increased thermal stability.;[Solution] To have a solution containing LiPF₆ contain a phosphoric acid ester amide represented by general formula (I) in such an amount that the molar ratio of the phosphoric acid ester amide relative to LiPF₆ is 0.001-2. (In the formula, m represents an integer of 1 or 2; each of R¹ and R² represents a branched or linear alkyl group having 1 to 6 carbon atoms and/or a hydrocarbon group having an unsaturated bond, provided that R¹ and R² may have a substituent that is selected from the group consisting of an alkoxy group, an amino group, an alkylthio group, a saturated heterocyclic group, an unsaturated heterocyclic group, and a fluorine atom, and R¹ and R² may combine together to form a 5 to 8 membered cyclic structure; and R³ represents a branched or linear alkyl group having 1 to 6 carbon atoms or a branched or linear fluorine-containing alkyl group having 1 to 6 carbon atoms)