Positive electrode active material and positive electrode including the same

A positive electrode active material comprising:

• a nickel-based lithium composite metal oxide having a Ni content of 80 atm % or greater among transition metals except lithium, wherein the nickel-based lithium composite metal oxide is in a form of a single particle or pseudo-single particle;
• and
• a coating layer positioned on a surface of the nickel-based lithium composite metal oxide, wherein the coating layer includes cobalt,
• wherein the positive electrode active material satisfies Equation 1 below:
• 1
• ≤
• XY
• /
• Z
• ≤
• 3
• [
• Equation
• ⁢
• 1
• ]
• wherein, X (mol %) is a number of moles of Co in the coating layer based on 100 moles of the nickel-based lithium composite metal oxide, Y (μm) is an average particle diameter of nodules of the nickel-based lithium composite metal oxide, and Z (μm) is D50 of the positive electrode active material, wherein Z is from 5 μm to 12 μm, and
• wherein the nickel-based lithium composite metal oxide is represented by Formula 2 below:
• wherein, M1 is Mn, Al, or a combination thereof, M2 is one or more selected from the group consisting of W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and 0.8≤a≤1.2, 0.8≤b<1, 0<c<0.2, 0<d<0.2, and 0≤e≤0.1.