POSITIVE ELECTRODE ACTIVE MATERIAL FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

A positive electrode active material for a nonaqueous electrolyte secondary battery includes particles of a lithium-transition metal composite oxide that contains nickel in the composition thereof and has a layered structure. The particles have an average particle size D SEM based on electron microscopic observation in a range of 1 µm to 7 µm in which a ratio D 50 /D SEM of a 50% particle size D 50 in volume-based cumulative particle size distribution to the average particle size based on electron microscopic observation is in a range of 1 to 4, and a ratio D 90 /D 10 of a 90% particle size D 90 to a 10% particle size D 10 in volume-based cumulative particle size distribution is 4 or less.