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 including nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al); and forming a lithium composite transition metal oxide by mixing the positive electrode active material precursor and a lithium source and performing calcination, wherein the positive electrode active material precursor includes nickel (Ni) in an amount of 60 mol % or more out of the entire metal element, and a molar ratio (Li/M) of lithium (Li) of the lithium source to the entire metal element (M) of the positive electrode active material precursor is greater than 1.1.