NICKEL MANGANESE COBALT COMPOSITE HYDROXIDE, METHOD FOR PRODUCING NICKEL MANGANESE COBALT COMPOSITE HYDROXIDE, LITHIUM NICKEL MANGANESE COBALT COMPOSITE OXIDE, AND LITHIUM ION SECONDARY BATTERY

A nickel manganese cobalt composite hydroxide, which is a precursor of positive electrode active material, and composed of secondary particles wherein primary particles containing nickel, manganese, and cobalt are aggregated, or composed of primary and secondary particles, wherein sodium content contained in nickel manganese cobalt composite hydroxide is less than 0.0005% by mass, and void ratio of particles of nickel manganese cobalt composite hydroxide is 20% to 50%. Also, ratio of average particle size of lithium nickel manganese cobalt composite oxide divided by average particle size of nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of lithium nickel manganese cobalt composite oxide selected randomly by scanning electron microscope, number that aggregation of secondary particles is observed is 5% or less with respect to total number of observed secondary particles.