Cathode active material for a lithium secondary battery containing phosphate fluoride and preparation method thereof

Provided is a cathode active material for a lithium secondary battery containing the compound of Formula 1 doped or coated with phosphate fluoride, prepared by adding phosphate fluoride to the precursor compound and subjecting to sintering and heat-treatment process, which has improved lifecycle and stability so that it can be used to improve the efficiency of the lithium secondary battery: Formula 1 Li Ni Co M' Mn() O wherein M', a, x, y and z are the same as defined in the specification.