Patent ID: 7150940

Claim:
A lithium ion secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein said positive electrode comprises a positive electrode active material, a conductive agent and a binder, said positive electrode active material comprises a lithium-containing composite oxide represented by the formula Li a (Co 1−x−y Mg x M y ) b O c , where M is at least one selected from Ni and Al, 0≦a≦1.05, 0.03≦x≦0.15, 0≦y≦0.25, 0.85≦b≦1.1 and 1.8≦c≦2.1, and an amount of said conductive agent contained in said positive electrode is not more than 3.0 parts by weight per 100 parts by weight of said positive electrode active material.