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

A method of preparing a positive active material for a rechargeable lithium battery, comprising:

• subjecting a first precursor to a first heat-treatment in an oxidizing gas atmosphere to obtain a first nickel-based oxide,
• subjecting a second precursor to a second heat-treatment in an oxidizing gas atmosphere to obtain a second nickel-based oxide,
• mixing the first nickel-based oxide and the second nickel-based oxide to yield a mixture, and subjecting the mixture to a third heat-treatment in an oxidizing gas atmosphere to obtain a positive active material comprising a first positive active material and a second positive active material,
• wherein the second nickel-based oxide comprises particles having a monolith structure, and
• wherein the second precursor is obtained by mixing a second composite metal hydroxide having a specific surface area of about 1 m2/g to about 30 m2/g, as measured using a BET method, with a lithium-based material.