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

A positive active material for a rechargeable lithium battery, the positive active material comprising:

• a first positive active material comprising a secondary particle in which a plurality of primary particles are aggregated, wherein at least one portion of the primary particles aggregated in the secondary particle has a radially arranged structure, and
• a second positive active material comprising a secondary particle in which a plurality of primary particles are aggregated,
• wherein,
• the first positive active material and the second positive active material are both nickel-based positive active materials,
• a particle diameter of the secondary particle of the first positive active material is larger than a particle diameter of the secondary particle of the second positive active material, and
• the second positive active material is coated with a boron compound, the second positive active material comprising:
• a first boron coating portion on an outer surface of the secondary particle, and
• a second boron coating portion present on surfaces of the primary particles inside the secondary particle, and the second boron coating portion is in an internal portion of the secondary particle that is inaccessible by effluent if washed with water,
• wherein the first boron coating portion is about 70 wt % to about 98 wt % and the second boron coating portion is about 2 wt % to about 30 wt %, each based on a total amount of the first boron coating portion and the second boron coating portion.