Abstract: A method for producing a positive electrode active material includes coating a surface of a solid solution active material represented by formula (1): Li1.5[Ni0.40Mn0.60Co0.40[Li]0.1]Oz, wherein X represents at least one selected from Ti, Zr and Nb, 0?e?0.5, a+b++c+d+e=1.5, 0.1?d?0.4, and 1.1?[a+b+c+e]?1.4, and z represents the number of oxygen atoms satisfying an atomic valence, with alumina; and preparing the solid solution active material. The preparing comprises mixing an organic acid salt of a transition metal having a melting point of 100° C. to 350° C., melting the mixture obtained in the first step at 100° C. to 350° C., subjecting the molten substance to pyrolysis at a temperature equal to higher than the melting point and calcining the pyrolysate obtained.

Abstract: A method capable of suppressing elution of a transition metal, particularly manganese, in a positive electrode active material for a non-aqueous electrolyte secondary battery provides a positive electrode active material for a non-aqueous electrolyte secondary battery, including: a solid solution active material represented by formula Li1.5[NiaMnbCoc[Li]d[X]e]Oz, wherein X represents at least one selected from Ti, Zr and Nb, 0?e?0.5, a+b+c+d+e=1.5, 0.1?d?0.4, and 1.1?[a+b+c+e]?1.4, and z represents the number of oxygen atoms satisfying an atomic valence; and an alumina layer on the surface of the solid solution active material and a region in which Al element is present on the side of the surface of the solid solution active material in the interface between the solid solution active material and the alumina layer.