| abstract |
The present invention relates to a positive electrode active material and a lithium ion secondary battery using the positive electrode active material. Provides high-durability positive electrode active materials and lithium-ion secondary batteries. The positive electrode active material is composed of the general formula Li (1+a) Ni x Co y Mn z W t O 2 (‑0.05≤a≤0.2, x=1‑y‑z‑t, 0≤y＜1,0 ≤z<1, 0<t≤0.03), wherein the element concentration inside the primary particle of the W element and at the grain boundary of the primary particle is averaged as t1, and the inside of the primary particle of the W element is When the standard deviation of the element concentration at the grain boundary of the primary particle is set to σ1, the following formula (1) is satisfied: σ1/t1≦0.92...(1). |