Composite positive electrode active materials, methods of preparing the composite positive electrode active materials, positive electrodes having the composite electrode active materials, and rechargeable lithium batteries including positive electrodes having the composite electrode active materials

A method of preparing a composite positive electrode active material, the method comprising:

• mixing a tungsten-doped nickel-based precursor, a lithium raw material, an aluminum raw material, and a boron raw material to obtain a mixture, wherein aluminum of the aluminum raw material is introduced in the mixture in an amount from about 0.1 parts by mole to about 1.45 parts by mole based on 100 parts by mole of a total metal in the tungsten-doped nickel-based precursor, and wherein boron of the boron raw material is introduced in the mixture in an amount from about 1.05 parts by mole to about 2 parts by mole based on 100 parts by mole of a total metal in the tungsten-doped nickel-based precursor;
• firing the mixture at a temperature of greater than about 720° C. to prepare a first positive electrode active material comprising a first lithium nickel-based composite oxide comprising tungsten, aluminum, and boron, wherein the aluminum of the first positive electrode active material derives from the aluminum raw material, and wherein the boron of the first positive electrode active material derives from the boron raw material;
• and
• mixing the first positive electrode active material and a second positive electrode active material comprising a second lithium nickel-based composite oxide having an average particle diameter D50 smaller than an average particle diameter D50 of the first positive electrode active material.