US Patent 11973216 Positive electrode active material and battery

A positive electrode active material includes positive electrode active material particles including a composite oxide with a hexagonal crystal structure. The composite oxide includes Li, Co, and at least one element M1 selected from the group consisting of Ni, Fe, Pb, Mg, Al, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn and Cr, and the at least one element M1 is provided on a surface of the positive electrode active material particles. An atomic ratio of a total amount of the at least one element M1 to an amount of Co on the surface of the positive electrode active material particles is from 0.6 to 1.3.