Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same

A positive active material for a rechargeable lithium battery, comprising

• secondary particles of a nickel-based transition metal oxide composed of an inner portion and an outer portion,
• wherein the inner portion has a dense structure having a higher density than the outer portion,
• the secondary particles of the nickel-based transition metal oxide have a plurality of protruding portions on the surface thereof, and
• the positive active material has an area ratio of 25% to 30% occupied by protrusions calculated by Equation 1 based on a cross-section of the secondary particles of the nickel-based transition metal oxide:
• [At-Ai]/At [Equation 1]
• wherein, in Equation 1,
• At is a total area of the secondary particle of the nickel-based transition metal oxide, and
• Ai is an area of an inner circle with a radius from the inner end of the vertically oriented primary particle constituting the protruding portions to the center of the secondary particle of the nickel-based transition metal oxide.