Positive electrode active material for nonaqueous electrolyte secondary batteries and method for producing positive electrode active material for nonaqueous electrolyte secondary batteries

A positive electrode active material for nonaqueous electrolyte secondary batteries, which contains a lithium-nickel-cobalt-zinc composite oxide powder that contains: lithium (Li); nickel (Ni); cobalt (Co); at least one element M selected from the group consisting of manganese (Mn), vanadium (V), magnesium (Mg), molybdenum (Mo), niobium (Nb), silicon (Si), titanium (Ti) and aluminum (Al); and zinc (Zn). With respect to the lithium-nickel-cobalt-zinc composite oxide powder, the elemental molar ratio (Li:Ni:Co:M) satisfies Li:Ni:Co:M = z:(1 - x - y):x:y (wherein 0.95 ≤ z ≤ 1.10, 0.05 ≤ x ≤ 0.35 and 0 ≤ y ≤ 0.10); the zinc content relative to Li, Ni, Co, the element M and oxygen is from 0.01% by mass to 1.5% by mass (inclusive); and at least a part of the surface thereof has a zinc solid-solved region where zinc is solid-solved.