Electrolytic solution for nonaqueous electrolytic solution secondary batteries and nonaqueous electrolytic solution secondary battery

An electrolytic solution for nonaqueous electrolytic solution secondary batteries, the electrolytic solution comprising:

• a nonaqueous solvent,
• an electrolyte dissolved in the nonaqueous solvent,
• (I) a difluoro ionic complex (1) represented by the general formula (1), and
• (II) at least one compound selected from the group consisting of cyclic sulfonic acid ester, cyclic sulfonic acid ester having an unsaturated bond, cyclic sulfuric acid ester, cyclic disulfonic acid ester, chain disulfonic acid ester, cyclic disulfonic acid anhydride, nitrile group-containing compound, silyl phosphate ester derivative, and silyl borate ester derivative:
• wherein 95 mol % or more of the difluoro ionic complex (1) is a difluoro ionic complex (1-Cis) in a cis conformation represented by the general formula (1-Cis),
• wherein in (1-Cis),
• wherein in the general formulas (1) and (1-Cis), A+ is any one selected from the group consisting of a metal ion, a proton, and an onium ion, and M is any one selected from the group consisting of Si, P, As, and Sb;
• F is a fluorine atom;
• O is an oxygen atom;
• t is 2 when M is Si, and t is 1 when M is P, As, or Sb;
• X is an oxygen atom or —N(R1)—;
• N is a nitrogen atom;
• R1 is a hydrocarbon group having 1 to 10 carbon atoms and optionally having a hetero atom and/or a halogen atom (the hydrocarbon group optionally having a branched-chain or ring structure when the number of carbon atoms is 3 or more);
• when X is —N(R1)—, and p is 0, X and W are bonded directly and optionally form a structure as shown in the general formulas (1-Cis-1) to (1-Cis-3) below;
• in the case of the general formula (1-Cis-2) below where the direct bond is a double bond, R1 is not present;
• Y is a carbon atom or a sulfur atom;
• q is 1 when Y is a carbon atom, and q is 1 or 2 when Y is a sulfur atom;
• W represents a hydrocarbon group having 1 to 10 carbon atoms and optionally having a hetero atom and/or a halogen atom (the hydrocarbon group optionally having a branched-chain or ring structure when the number of carbon atoms is 3 or more), or —N(R2)—;
• wherein, R2 represents a hydrogen atom, an alkaline metal, or a hydrocarbon group having 1 to 10 carbon atoms and optionally having a hetero atom and/or a halogen atom;
• when the number of carbon atoms is 3 or more, R2 optionally has a branched-chain or ring structure;
• and
• p is 0 or 1, q is an integer of 0 to 2, r is an integer of 0 to 2, and p+r≥1: