POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE, NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, AND METHOD FOR PRODUCING POSITIVE ELECTRODE ACTIVE MATERIAL

A positive electrode active material according to one aspect of the present disclosure is used in a nonaqueous electrolyte secondary battery (10) and is characterized by having a crystal structure that belongs to a space group R-3m, being represented by a composition formula LixNayNi1-a-bMnaXbOc, where X is at least one selected from the group consisting of transition metal elements other than Li, Na, Ni, and Mn and representative elements, 0.80≤x≤1.15, 0