| abstract |
A nickel cobalt aluminum composite hydroxide, which is a precursor of a positive electrode active material, and which is composed of secondary particles to which primary particles containing a nickel, a cobalt, and an aluminum are aggregated, or composed of the primary particles and the secondary particles, wherein a sodium content contained in the nickel cobalt aluminum composite hydroxide is less than 0.0005% by mass. Also, a ratio of an average particle size of a lithium nickel cobalt aluminum composite oxide divided by an average particle size of the nickel cobalt aluminum composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of the lithium nickel cobalt aluminum composite oxide 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. |