Patent ID: 7985502

Claim:
A nonaqueous electrolytic solution for a lithium secondary battery, comprising: an electrolyte salt dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution comprises from 0.01 to 10% by weight of at least one formic ester compound selected from the group consisting of formulae (I) to (III), V and VIII: wherein X 1 to X 5 are each independently a hydrogen atom, a halogen atom, a C 1 to C 6 linear or branched alkyl group, a cyclohexyl group or a phenyl group; wherein R 1 is a hydrogen atom, a C 1 to C 12 linear or branched alkyl group, a C 3 to C 8 cycloalkyl group or a C 6 to C 12 aryl group; and Z is a C 2 to C 12 saturated or unsaturated hydrocarbon group; (HCOO) m —W—(OCOR 1 ) n (III) wherein m is an integer of 1 to 4; n is an integer of 0 to 3; and W is a C 3 to C 8 (m+n)-valent linking group consisting of carbon atoms and hydrogen atoms; (m+n) is 3 or 4; and R 1 is defined above; wherein R 2 is a C 6 to C 20 linear or branched alkyl group; R 4 and R 5 are each, independently a hydrogen atom or a C 1 to C 8 alkyl group; R 9 is a C 1 to C 20 linear or branched alkyl group, a C 1 to C 20 linear or branched alkenyl group or a C 1 to C 20 linear or branched alkynyl group; and n is an integer of 1 to 10.