POSITIVE ELECTRODE ACTIVE MATERIAL FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERIES, AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

Provided are: a nonaqueous electrolyte secondary battery which is high capacity, and exhibits improved initial charge/discharge efficiency and charge/discharge cycle properties; and a positive electrode active material to be used in the nonaqueous electrolyte secondary battery. A positive electrode active material which is to be included in this nonaqueous electrolyte secondary battery and contains a lithium-containing complex oxide having a prescribed composition which has a layered evaporitic structure, wherein: the lithium-containing complex oxide contains secondary particles formed by clumping primary particles with one another; and a sulfonic acid compound represented by general formula I, one or more types of element selected from Ca and Sr, and one or more types of element selected from W, Mo, Ti, Si, Nb and Zr are present on the surface of the secondary particles or at the interface between the primary particles. (In the formula, A is a Group 1 element or a Group 2 element, R is a hydrocarbon group, and n is 1 or 2.)