Positive electrode active material including particle comprising crystal structure changing from a layered structure to a spinel structure, method of manufacturing the positive electrode active material, and non-aqueous electrolyte secondary battery using the positive electrode active material

A positive electrode active material comprising:

• a lithium-excess lithium-transition metal composite oxide particle represented by the chemical formula Li1+x−sMn1−x−yMyO2−t, where 0<x<0.33, 0<y<0.66, 0<s<0.3, 0<t<0.15, and M is at least one transition metal other than manganese;
• and
• the lithium-excess lithium-transition metal composite oxide particle comprising an inner portion having a layered structure and a surface adjacent portion having a crystal structure changing from a layered structure to a spinel structure from an inner part thereof toward a surface part thereof, and the layered structure and the spinel structure having an identical ratio of the Mn and the M in the chemical formula.