Nonaqueous electrolytic solution and lithium ion secondary battery

1. A nonaqueous electrolytic solution comprising a nonaqueous solvent, an electrolyte salt comprising a lithium salt, and a difluoroboron complex compound represented by the following general formula (1):

wherein R 1 and R 2 each independently represent a substituted or unsubstituted alkyl group having 1-6 carbon atoms, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkoxy group, and R 3 represents a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

2. The nonaqueous electrolytic solution according to claim 1 , wherein a content of the difluoroboron complex compound is in the range of 0.01 to 10% by mass based on a total mass of the nonaqueous electrolytic solution.

3. The nonaqueous electrolytic solution according to claim 1 , wherein in the formula (1),

the substituted or unsubstituted alkyl group having 1-6 carbon atoms is an unsubstituted alkyl group having 1-6 carbon atoms or an alkyl group having 1-6 carbon atoms with one or more hydrogen atoms of the alkyl group replaced with a substituent selected from the group consisting of a fluorine atom, a cyano group, an ester group having 1-5 carbon atoms, an alkoxy group having 1-5 carbon atoms, an aryl group, and a heteroaryl group,

the substituted or unsubstituted aryl group is an unsubstituted aryl group or an aryl group with one or more hydrogen atoms of the aryl group replaced with a substituent selected from the group consisting of an alkyl group having 1-5 carbon atoms, a fluorine atom, a cyano group, and an alkoxy group having 1-5 carbon atoms,

the substituted or unsubstituted heteroaryl group is an unsubstituted heteroaryl group or a heteroaryl group with one or more hydrogen atoms of the heteroaryl group replaced with a substituent selected from the group consisting of an alkyl group having 1-5 carbon atoms, a fluorine atom, a cyano group, and an alkoxy group having 1-5 carbon atoms, and

the substituted or unsubstituted alkoxy group is an unsubstituted alkoxy group having 1-5 carbon atoms or an alkoxy group having 1-5 carbon atoms with one or more hydrogen atoms of the alkoxy group replaced with a substituent selected from the group consisting of a fluorine atom, a cyano group, an aryl group, and a heteroaryl group.

4. The nonaqueous electrolytic solution according to claim 1 , wherein in the formula (1),

R 1 and R 2 are each independently a group selected from the group consisting of a methyl group, a trifluoromethyl group, a pentafluoroethyl group, a phenyl group, a 2-thienyl group, a 2-furanyl group, a 2-fluorophenyl group, a pentafluorophenyl group, a 4-fluorophenyl group, a 2,4-difluorophenyl group, a 4-cyanophenyl group, an ethoxy group, and a methoxy group, and

R 3 is an atom or a group selected from the group consisting of a hydrogen atom, a phenyl group, a 2-thienyl group, a 4-fluorophenyl group, a 2,4-difluorophenyl group, and a pentafluorophenyl group.

5. The nonaqueous electrolytic solution according to claim 1 , further comprising at least one additive compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesultone, maleic anhydride, and 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide.

6. The nonaqueous electrolytic solution according to claim 5 , wherein a content of the additive compound is in the range of 0.01 to 10% by mass based on a total mass of the nonaqueous electrolytic solution.

7. The nonaqueous electrolytic solution according to claim 1 , comprising a carbonate as the nonaqueous solvent.

8. The nonaqueous electrolytic solution according to claim 1 , wherein a concentration of the electrolyte salt is in the range of 0.1 to 3 mol/L.

9. A lithium ion secondary battery comprising: a positive electrode comprising a positive electrode active material capable of intercalating and deintercalating a lithium ion; a negative electrode comprising a negative electrode active material capable of intercalating and deintercalating a lithium ion; and the nonaqueous electrolytic solution according to claim 1 .

10. The lithium ion secondary battery according to claim 9 , wherein the negative electrode active material comprises at least one selected from the group consisting of elementary silicon, a silicon oxide, and a carbonaceous material.