POSITIVE ELECTRODE ACTIVE MATERIAL AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a bimodal-type positive electrode active material including a first lithium composite oxide as a small particle and a second lithium composite oxide as a large particle, wherein the positive electrode active material may uniformly improve the particle stability of the small particle and the large particle by controlling a slope of a concentration gradient in which cobalt in the small particle and the large particle decreases from a surface portion toward a central portion, a positive electrode including the positive electrode active material, and a lithium secondary battery using the positive electrode.