| abstract |
A lithium ion secondary battery comprising anpositive electrode, a negative electrode and a non-aqueousnelectrolyte, wherein the positive electrode comprises anpositive electrode active material, a conductive agent and anbinder, the positive electrode active material comprises anlithium-containing composite oxide represented by the formulanLi a (Co 1-x-y Mg x M y ) b O c , where M is at least one selected from Ninand Al, 0 ≦ a ≦ 1.05, 0.03 ≦ x ≦ 0.15, 0 ≦ y ≦ 0.25,n0.85 ≦ b ≦ 1.1 and 1.8 ≦ c ≦ 2.1, and the amount of thenconductive agent contained in the positive electrode is notnmore than 3.0 parts by weight per 100 parts by weight of thenpositive electrode active material. |