Composite positive electrode active material, method of preparing the same, positive electrode including composite positive electrode active material,and lithium battery including positive electrode

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

• mixing a precursor for forming a composite positive active material represented by Formula 1 to obtain a precursor mixture;
• pulverizing the precursor mixture to obtain a pulverized product;
• first thermally treating the pulverized product to obtain a first thermal treatment product;
• and
• cooling the first thermal treatment product, wherein the cooling comprises cooling at a cooling rate of about 500° C. per minute to about 900° C. per minute,
• LiaNibCOcMndMeO2 Formula 1
• wherein, in Formula 1, M is zirconium, aluminum, rhenium, vanadium, chromium, iron, gallium, silicon, boron, ruthenium, titanium, niobium, molybdenum, magnesium, or platinum,
• 1.1≤a≤1.3, b+c+d+e≤1, 0≤b≤0.3, 0≤c≤0.3, 0<d≤0.6, and 0≤e≤0.1, and
• wherein, through atomic interdiffusion of lithium and the metal, the composite positive active material has
• a uniform distribution of lithium excess regions, and a uniform degree of disorder of metal cations, and
• the metal cations have a mixed disordered, irregular arrangement at an atomic scale and a disordered cation structure,
• a ratio of an intensity of a (003) peak to an intensity of a (104) peak is about 0.87 to about 1.11, when the composite positive active material is analyzed by X-ray diffraction using Cu Kα radiation, and
• wherein a full width at half-maximum of a diffraction peak between 43º and 45° 2θ of the composite positive active material is about 0.2° to about 0.32°, when the composite positive active material is analyzed by X-ray diffraction using Cu Kα radiation.