LITHIUM-NICKEL BASED CATHODE ACTIVE MATERIAL, METHOD FOR PREPARING SAME, AND LITHIUM SECONDARY BATTERY INCLUDING SAME

The present invention relates to a cathode active material comprising: a lithium-nickel based transition metal composite oxide which is doped with an alkali earth metal having an oxidation state of +2; and a phosphorous oxide coating layer formed on the outer surface of the composite oxide, such that a lithium by-product is reduced and structural stability is improved. Accordingly, a secondary battery comprising the cathode active material has an excellent capacity property and at the same time, has improved structural stability during charging and discharging, and has a superior lifespan by suppressing swelling. Thus, the present invention can be easily applied to industries that require the present invention, particularly, to industries that require high capacity and a long-term lifespan of an electric vehicle and the like.