Positive electrode active material for nonaqueous electrolyte secondary batteries, and production method thereof

A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material being represented by a general formula (1):

• LiaNi1-x-yCoxMyWzO2+α,
• where 0≤x≤0.35, 0≤y≤0.35, 0.0005≤z≤0.030, 0.97≤a≤1.25, 0≤α≤0.20, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al, wherein:
• a lithium-metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles is a base material,
• the positive electrode active material has voids between the primary particles of the lithium-metal composite oxide as the base material and a void content measured by image analysis of any cross section of the secondary particles with a scanning electron microscope (SEM) is 0.15 to 3%,
• a compound containing lithium and tungsten is formed on a surface of the primary particles of the lithium-metal composite oxide as the base material, the compound containing lithium and tungsten is present on the surface of the primary particles of the lithium-metal composite oxide in both forms of thin film having a film thickness of 1 to 100 nm and fine particles having a particle size of 1 to 200 nm,
• a specific surface area of the positive electrode active material, measured by a BET method, is 0.9 to 1.5 m2/g, and
• when the voids between the primary particles at any 20 or more points are EDX analyzed in transmission-type electron microscope observation of a cross section of the secondary particles, tungsten is detected at 50% or more of the number of the voids analyzed.