| abstract |
A solid solution lithium-containing transition metal oxide, including a compound indicated by chemical formula (1). Chemical formula 1: Li 1.5 [Ni a Co b Mn c [Li] d ]O 3 . (In formula, a, b, c, and d fulfill the relationships 0<a≦0.75, 0≦b≦0.5, 0<c≦1.0, 0.05≦d≦0.25, and a+b+c+d=1.5.) A dQ/dV curve, obtained by differentiating a discharge side open circuit voltage curve obtained by charging/discharging a lithium ion secondary battery using said compound as the positive electrode active material therefor, fulfills numerical formula (1). Numerical formula 1: A/B≦1.0 (in formula, A indicates the dQ/dV value in a peak (A) positioned between 3.0-3.5 V in the dQ/dV curve. B indicates the dQ/dV value in a peak (B) positioned between 3.5-4.0 V in the dQ/dV curve. |