Positive electrode active material for non-aqueous electrolyte secondary batteries, production process therefor, and non-aqueous electrolyte secondary battery

A positive electrode active material for a non-aqueous electrolyte secondary battery, the positive electrode active material comprising hexagonal lithium-nickel-cobalt-manganese composite oxide particles represented by the general formula:

• Li1+sNixCoyMnzMtO2
• wherein:
• s, x, y, z, and t in the formula fall within the ranges of:
• −0.05≤s≤0.20;
• 0.1≤x≤0.7;
• 0.1≤y≤0.5;
• 0.1≤z≤0.5;
• and 0≤t≤0.05, and x, y, z, and t meet x+y+z+t=1,
• M in the formula represents one or more additive elements selected from the group consisting of Ca, Mg, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W,
• the lithium-nickel-cobalt-manganese composite oxide particles have a layered structure comprising secondary particles with aggregated primary particles,
• the secondary particles each comprises an outer-shell part that has a high manganese concentration and a central part that has a low manganese concentration that is lower than the high manganese concentration in the outer-shell part of the secondary particle,
• the primary particles constitute the outer-shell parts of the secondary particles,
• each of the primary particles comprises an outer peripheral part that has a low manganese concentration and an inner part that has a high manganese concentration, and
• a ratio of the high manganese concentration in the inner part of the primary particle to the low manganese concentration in the outer peripheral part of the primary particle is in a range of from 1.5 to 2.5.