POSITIVE ELECTRODE ACTIVE MATERIAL, METHOD FOR PREPARING SAME, AND POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY BOTH COMPRISING SAME

A positive electrode active material according to the present invention is a positive electrode active material including a lithium nickel-based oxide in the form of a single particle which is composed of one single nodule, or a pseudo-single particle which is a composite of 30 or fewer nodules, wherein the lithium nickel-based oxide includes cobalt (Co) and aluminum (Al), and concentration ratios of cobalt (Co) and aluminum (Al) on the surface of the lithium nickel-based oxide which are measured by Energy Dispersive X-ray Spectroscopy (EDX) respectively satisfy Equations 1 and 2 below: (Concentration ratio of Co in nodule to positive electrode active material)≤(Concentration ratio of Co at nodule interface to positive electrode active material)≤ (Concentration ratio of Co on surface of lithium nickel-based oxide particle to positive electrode active material) (Concentration ratio of Al on surface of lithium nickel-based oxide particle to positive electrode active material)≤ (Concentration ratio of Al at nodule interface to positive electrode active material)