Method of Preparing Positive Electrode Active Material for Secondary Battery

A method of preparing a positive electrode active material for a secondary battery includes preparing a positive electrode active material precursor containing 60 mol % or more of nickel (Ni) among total metals, mixing the positive electrode active material precursor and a lithium raw material source and performing primary pre-sintering in an oxidizing atmosphere to form a pre-sintered product, and performing secondary main sintering on the pre-sintered product in an air atmosphere to form a lithium transition metal oxide.