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

A positive electrode active material characterized by containing a lithium transition metal compound that contains, relative to the total number of moles of metal elements other than Li, from 80% by mole to 94% mole (inclusive) of Ni and from 0.1% by mole to 0.6% by mole (inclusive) of Nb, and the amount of Nb (n1) in a first sample solution is obtained by adding 0.2 g of the lithium transition metal compound into an aqueous hydrochloric acid solution composed of 5 mL of pure water and 5 mL of 35% hydrochloric acid and the amount of Nb (n2) in a second sample solution that is obtained by immersing a filter that is used for filtration of the first sample solution into a fluoronitric acid composed of 5 mL of 46% hydrofluoric acid and 5 mL of 63% nitric acid satisfy the condition 75%≤n1/(n1+n2)