CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

A cathode active material for a lithium secondary battery according to embodiments of the present invention has a high-nickel composition and includes a lithium-nickel composite metal oxide particle in which lithium, nickel and a metal having an oxidation number of +2 are combined in a predetermined range. A cation disorder caused when a nickel ion is present at a lithium-ion site is reduced to improve structural stability of the cathode active material. An initial capacity and a battery efficiency of a lithium secondary battery can be improved using the cathode active material.