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 a positive electrode active material and is composed of secondary particles to which primary particles containing a nickel, manganese, and cobalt are aggregated, or composed of the primary and secondary particles, wherein a sodium content contained in the nickel manganese cobalt composite hydroxide is less than 0.0005% by mass, and a void ratio of particles is more than 50% to 80%. Also, a ratio of an average particle size of a lithium nickel manganese cobalt composite oxide divided by an average particle size of the nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles selected randomly by a scanning electron microscope, a number that an aggregation of secondary particles is observed is 5% or less with respect to a total number of observed secondary particles.