Positive active material for rechargeable lithium battery, preparing method thereof and rechargeable lithium battery comprising positive electrode including positive active material

A positive active material for a rechargeable lithium battery, a preparing method thereof, and a rechargeable lithium battery including the same are provided. The positive active material includes: a first positive active material in a form of secondary particles in which a plurality of primary particles are aggregated, wherein at least a portion of the primary particles have a radially arranged structure, and a second positive active material having a monolithic structure, wherein both the first positive active material and the second positive active material are nickel-based positive active materials, each of the first positive active material and the second positive active material is coated with cobalt, and a maximum roughness of the surface of the second positive active material is greater than or equal to about 15 nm.