Method for producing positive electrode active material for nonaqueous electrolyte secondary battery

A method of producing a positive electrode active material for nonaqueous electrolyte secondary batteries, comprising

• a water washing step of mixing, with water, a lithium-nickel composite oxide powder represented by a general formula:
• LizNi1-x-yCoxMyO2, where 0≤x≤0.35, 0≤y≤0.35, and 0.95≤z≤1.30 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al, the lithium-nickel composite oxide powder having a layered crystal structure composed of primary particles and secondary particles formed by aggregation of the primary particles to form a slurry, and the water washing step including washing the lithium-nickel composite oxide powder with the water, and then subjecting the slurry to solid-liquid separation to obtain a washed cake constituted by washed lithium-nickel composite oxide particles;
• a mixing step of mixing a tungsten compound powder not containing lithium with the washed cake to obtain a tungsten-containing mixture;
• and
• a heat treatment step of heating the tungsten-containing mixture, wherein
• the heat treatment step includes:
• a first heat treatment step of heating the tungsten-containing mixture to allow a lithium compound present on a surface of the primary particles of the washed lithium-nickel composite oxide to react with the tungsten compound so as to dissolve the tungsten compound therein, thereby forming lithium-nickel composite oxide particles with tungsten dispersed on the surface of the primary particles;
• and
• subsequent to the first heat treatment step, a second heat treatment step of performing heat treatment at a higher temperature than in the first heat treatment step to form lithium-nickel composite oxide particles with a lithium tungstate compound formed on the surface of the primary particles of the lithium-nickel composite oxide.