| abstract |
A positive electrode active material capable of producing a nonaqueous electrolyte secondary battery having high energy density and excellent charge / discharge cycle performance, and a positive electrode for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary using the same Provide batteries. The composition formula is Li a Mn 0.5-x Ni 0.5-y M x + y O 2 (where 0.98 ≦ a <1.1, −0.1 ≦ xy ≦ 0.1, M Is a positive electrode active material containing a composite oxide represented by (elements other than Li, Mn, Ni). In addition, the composition formula Li w Mn x ′ Ni y ′ Co z ′ O 2 (where x ′, y ′, and z ′ are points (x ′, y ′, z ′) on the ternary phase diagram). (0.51, 0.49, 0), point B (0.45, 0.55, 0), point C (0.25, 0.35, 0.4) and point D (0.31,0) .29,0.4) is a value in a range existing on or in the line of the rectangular ABCD having a vertex, and is represented by 0 ≦ w / (x ′ + y ′ + z ′) ≦ 1.30) A positive electrode active material containing a composite oxide. [Selection] Figure 1 |