Disclosed is a lithium ion secondary battery having a positive electrode, a negative electrode and a non-aqueous electrolyte composition (electrolytic solution), characterized in that: the positive electrode includes a positive electrode active material represented by: aLi[Li1/3M12/3]O2.(1−a)LiM2O2 (where M1 represents at least one kind of metal element selected from the group consisting of Mn, Ti, Zr and V; M2 represents at least one kind of metal element selected from the group consisting of Ni, Co, Mn, Al, Cr, Fe, V. Mg and Zn; and a represents a composition ratio and satisfies a relationship of 0