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 an embodiment of the present invention has a structure of a lithium-nickel-based composite oxide. A crystallite size ratio obtained by an XRD analysis is in a range from 1.5 to 3.5, and D() exceeds 200 nm. The crystallite size is adjusted to promote movement of lithium ions in the cathode active material so that an initial efficiency of a lithium secondary battery is improved.