| abstract |
A positive electrode active material for lithium ion secondary batteries, said positive electrode active material containing a lithium nickel composite oxide that has a hexagonal layered structure, while being composed of a single primary particle and/or a secondary particle where a plurality of primary particles aggregate. With respect to this positive electrode active material for lithium ion secondary batteries, the metal elements constituting the lithium nickel composite oxide include lithium (Li) and nickel (Ni), and optionally at least one element M (M) that is selected from the group consisting of Co, Mn, Al, V, Mg, Mo, Ca, Cr, Zr, Ti, Nb, Na, K, W, Fe, Zn, B, Si, P and Ta; the amount-of-substance ratio among the metal elements is expressed by Li:Ni:M = a:b:c (wherein 0.95 ≤ a ≤ 1.10, 0.30 ≤ b ≤ 1.00, 0.00 ≤ c ≤ 0.70 and (b + c) = 1); and if a region wherein the crystal misorientation is within 15° is taken as one crystal plane in a cross-section of a particle of the positive electrode active material, the area ratio of the crystal plane that has the largest area within the particle is 80% or more. |