Lithium ion secondary battery positive electrode active material, and production method thereof

Provided is a lithium ion secondary battery positive electrode active material with excellent cycle characteristics and rate characteristics even when charging has been performed at high voltages. This lithium ion secondary battery positive electrode active material comprises particles (III) having, on the surface of a lithium-containing composite oxide, a covering layer containing a metal oxide (I) comprising at least one metallic element chosen from the group consisting of group 3 elements, group 13 elements and lanthanoids in the period table, and a compound (II) containing Li and P, and is characterized in that the atomic ratio (P/metallic elements) of the particles (III) in the layer within 5nm of the surface is 0.03-0.45.