POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY

A positive electrode active material for a lithium ion secondary battery, the positive electrode active material including a lithium-nickel composite oxide having a hexagonal layered structure and configured by particles including at least either single primary particles or secondary particles with a plurality of aggregated primary particles, wherein the particles of the positive electrode active material have a cross section having an area proportion of a crystal face having a maximum area in the particle of 80% or more when one crystal face is defined as a region having a crystal misorientation of 15° or less.