Patent ID: 7691539

Claim:
A non-aqueous secondary battery having a positive electrode comprising, as the positive electrode active material, a combination of a lithium element and a complex metal oxide, a negative electrode comprising carbonaceous material having a graphite crystalline structure, and a non-aqueous electrolytic solution comprising an electrolyte dissolved in a non-aqueous solvent comprising a combination of a cyclic carbonate and a linear carbonate wherein the ratio of cyclic carbonate to linear carbonate ranges from 1:4 to 7:3 and which contains a disulfide derivative having the following formula: R 1 —S—S—R 2 wherein each of R 1 and R 2 independently represents a phenyl group, a benzyl group, a tolyl group, a pyridyl group, a pyrimidyl group, an alkyl group having 1 to 12 carbon atom, or a cycloalkyl group having 3 to 6 carbon atoms, provided that each group may have one or more substituent groups in an amount of 0.02 to 0.9 weight % based on the amount of the electrolytic solution, whereby the discharge capacity retention after 50 discharge cycles is maintained at least 85% of the discharge capacity measured at a first discharge procedure and is higher than a discharge capacity retention after 50 discharge cycles measured on an equivalent non-aqueous electrolytic solution not containing the disulfide derivative by at least 4%.