LITHIUM COMPOSITE OXIDE, AND CATHODE ACTIVE MATERIAL FOR SECONDARY BATTERY, COMPRISING SAME

A cathode active material of the present invention comprises a lithium nickel-based composite oxide comprising secondary particles formed by the aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M′ and a fluoride anion (F), respectively, which are contained in a fluorine-based compound, and the average Ni occupancy in the Li 3a site, obtained through Rietveld refinement using X-ray diffraction of the secondary particles, is 1.1-1.5%.