Method of producing positive electrode active material for nonaqueous electrolyte secondary battery

A method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, comprising:

• providing nickel-containing composite oxide particles having a ratio 1D90/1D10 of a 90% particle size 1D90 to a 10% particle size 1D10 in volume-based cumulative particle size distribution of 3 or less;
• mixing the composite oxide particles and a lithium compound to obtain a first mixture;
• subjecting the first mixture to a first heat treatment at a first temperature and a second heat treatment at a second temperature higher than the first temperature to obtain a first heat-treated material;
• and
• dissociating from the first heat-treated material the positive electrode active material,
• wherein the positive electrode active material comprises lithium-transition metal composite oxide particles being single particles,
• wherein the lithium-transition metal composite oxide particles have a ratio 2D90/2D10 of a 90% particle size 2D90 to a 10% particle size 2D10 in volume-based cumulative particle size distribution is 4 or less, and
• wherein a molar ratio of nickel in a composition of the lithium-transition metal composite oxide to a total molar number of metals other than lithium is 0.3 to 0.6.