Patent ID: 7695863

Claim:
A nonaqueous electrolytic solution for lithium secondary batteries, wherein the nonaqueous electrolytic solution comprises an electrolyte salt dissolved in a nonaqueous solvent, from 0.01 to 10% by weight of a dicarbonyl compound according to formula (II), and at least one member selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone and glycol sulfite in which at least one is present in an amount of from 0.01 to 10% by volume of the nonaqueous solvent: wherein R 1 represents a hydrogen atom, a C 1 to C 12 alkyl group, a C 3 to C 8 cycloalkyl group, a C 2 to C 12 alkenyl group, a C 2 to C 12 alkynyl group or an unsubstituted or substituted phenyl group; X represents an OR 2 group, wherein R 2 represents a C 3 to C 8 cycloalkyl group, a C 2 to C 12 alkenyl group, a C 2 to C 12 alkynyl group or an unsubstituted or substituted phenyl group; Y and Z each independently represent a hydrogen atom, an R 2 group, an OR 2 group, a COR 2 group or a CH 2 COR 2 group, wherein R 2 is the same as defined above; and n represents an integer from 1 to 6; wherein R 1 and X, R 1 and Y, R 1 and Z, X and Y, X and Z, Y and Z, R 1 , Y and Z, or R 1 , X, Y and Z, may bond to each other to form a ring, with the proviso that when n is 2 or more, Y and Z each bond to a different carbon atom and are independent from each other.