Positive electrode active material for lithium ion secondary battery, method of manufacturing positive electrode active material for lithium ion secondary battery, and lithium ion secondary battery

A method of manufacturing a positive electrode active material for a lithium ion secondary battery, comprising:

• a drying step of heating a metal composite hydroxide at 105° C. or higher and 120° C. or lower to obtain a dried metal composite hydroxide;
• a mixing step of mixing the dried metal composite hydroxide with a lithium compound to form a lithium mixture;
• and
• a firing step of firing the lithium mixture formed in the mixing step at a temperature of 650° C. or higher and 900° C. or lower in an oxidizing atmosphere;
• wherein the metal composite hydroxide contains nickel (Ni), cobalt (Co), and an element M in a mass ratio of Ni:Co:M=1−x−y:x:y (wherein 0≤x≤0.35, 0≤y≤0.35, and the element M is at least one element selected from Mg, Ca, Al, Si, Fe, Cr, Mn, V, Mo, W, Nb, Ti, Zr, and Ta), and
• wherein a specific surface area of a positive electrode active material for the lithium ion secondary battery obtained after the firing step is 0.7 m2/g or more and 2.0 m2/g or less.