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

This positive electrode active material for nonaqueous electrolyte secondary batteries includes a Ni-containing lithium composite oxide A and Ni-containing lithium composite oxide B. The Ni-containing lithium composite oxide A contains at least 55 mol% of Ni relative to the total number of mols of metal elements other than Li. The Ni-containing lithium composite oxide B contains Ti and Ni. The Ni content in the Ni-containing lithium composite oxide B is at least 55 mol% relative to the total number of mols of metal elements other than Ti and Li. The Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B have a prescribed average first particle diameter and a prescribed average second particle diameter, respectively, and the ratio between the Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B is, in mass ratio, 5:95-55:45. By using this positive electrode active material, a higher capacity nonaqueous electrolyte secondary battery can be provided that has suppressed occurrence of resistance increase and internal short circuits.