| abstract |
A positive electrode active material for a lithium ion secondary battery comprising a lithium nickel composite oxide having a layered structure of a hexagonal system and comprising at least one of a single primary particle and a secondary particle in which a plurality of primary particles are aggregated, the lithium nickel composite oxide The metal elements constituting the lithium (Li) and nickel (Ni), and optionally Co, Mn, Al, V, Mg, Mo, Ca, Cr, Zr, Ti, Nb, Na, K, W, Fe, Zn , B, Si, P, and at least one element M(M) selected from the group consisting of Ta, wherein the ratio of the amount of the metal element is Li:Ni:M=a:b:c (provided that 0.95≤ A ≤ 1.10, 0.30 ≤ b ≤ 1.00, 0.00 ≤ c ≤ 0.70, b + c = 1), in the particle cross section of the positive electrode active material, in the case where the region where the crystal orientation difference is within 15° is used as one crystal plane , A positive electrode active material for a lithium ion secondary battery in which an area ratio of a crystal plane having a maximum area in the particle is 80% or more. |