Positive electrode active material, preparing method therefor, and lithium secondary battery including same

A method of preparing a positive electrode active material, comprising

• (i) forming a positive electrode active material through a heat treatment process;
• and
• (ii) washing the positive electrode active material with washing water including at least one of a water-soluble ammonium-based organic compound and a water-soluble amine-based organic compound,
• wherein the positive electrode active material comprises a core including lithium nickel composite oxide represented by Chemical Formula 1:
• LiaNixCoyMzO2 [Chemical Formula 1]
• wherein, in Chemical Formula 1,
• M is one or two or more a metal element selected from Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce,
• 0.9≤a≤1.05,
• 0.7≤x<1.0,
• 0.01≤y≤0.3,
• 0.01≤z≤0.3, and
• x+y+z=1,
• wherein the prepared positive electrode active material has a surface layer present on the core, the surface layer includes at least one of a water-soluble ammonium-based organic compound and a water-soluble amine-based organic compound derived from the washing water, and
• wherein an area of the surface layer is 0.1% to 10% of the total surface area of the core.