| abstract |
[PROBLEMS] To provide a positive electrode active material layered compound for a lithium ion secondary battery that combines a high energy density and a high cycle characteristic. [MEANS FOR SOLVING PROBLEMS] Li-ion secondary battery, the positive electrode active material of the present invention, the space as a lithium ion secondary battery positive electrode active material comprising a layered structure compound belonging to the group R-3m, the layered structure compound, the composition formula: Li 1 + a M1O 2 +? Wherein M1 is at least Ni as a metal element other than Li, -0.03? A? 0.10, and -0.1 <?? 0.1, and the ratio of Ni in M1 is 70 , The site occupancy of the transition metal in the 3a site by structural analysis by the Rietveld method is less than 2%, and the content of residual lithium hydroxide in the positive electrode active material is 1 mass% or less. |