Positive electrode active material for secondary battery and secondary battery including the same

1. A positive electrode active material for a secondary battery, the positive electrode active material comprising:

a core including a lithium cobalt oxide; and

a lithium-metal oxide and a metal oxide, which include at least one metal selected from the group consisting of aluminum (Al), magnesium (Mg), tungsten (W), molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), iron (Fe), vanadium (V), chromium (Cr), barium (Ba), calcium (Ca), and niobium (Nb), on a surface of the core,

wherein the lithium-metal oxide is a heat fused material of the lithium cobalt oxide and the metal oxide, and

wherein the core is a heat fused material of the lithium cobalt oxide particles having first lithium cobalt oxide particles having an average particle diameter of 2 μm or less and second lithium cobalt oxide particles having an average particle diameter of 6 μm or more,

wherein the first lithium cobalt oxide particles, are melted to be fused to the second lithium cobalt oxide particles.

2. The positive electrode active material for a secondary battery of claim 1 , further comprising the lithium-metal oxide and the metal oxide in a region corresponding to a distance from the surface of the core of 0% or more to less than 100% of a total distance from the surface of the core to a center thereof.

3. The positive electrode active material for a secondary battery of claim 1 , wherein the lithium-metal oxide and the metal oxide comprise at least one metal selected from the group consisting of Al, Mg, and Ti.

4. The positive electrode active material for a secondary battery of claim 1 , wherein the lithium-metal oxide and the metal oxide comprise Al.

5. The positive electrode active material for a secondary battery of claim 1 , wherein the core comprises irregularities on the surface thereof.

6. The positive electrode active material for a secondary battery of claim 5 , wherein the irregularities comprise a concave portion and a convex portion, and

the concave portion is partially or entirely buried with the lithium-metal oxide and the metal oxide.

7. The positive electrode active material for a secondary battery of claim 1 , wherein an average particle diameter (D 50 ) of the positive electrode active material is in a range of 2 μm to 20 μm.

8. A method of preparing the positive electrode active material for a secondary battery of claim 1 , the method comprising:

performing a surface treatment of particles of a lithium cobalt oxide with a metal-containing raw material, and sequentially performing a primary heat treatment at 200° C. to 500° C. and a secondary heat treatment at 600° C. to 1200° C.;

the metal comprises at least one element selected from the group consisting of aluminum (Al), magnesium (Mg), tungsten (W), molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), iron (Fe), vanadium (V), chromium (Cr), barium (Ba), calcium (Ca), and niobium (Nb).

9. A positive electrode for a secondary battery, the positive electrode comprising the positive electrode active material of claim 1 .

10. A lithium secondary battery comprising the positive electrode of claim 9 .

11. A battery module comprising the lithium secondary battery of claim 10 as a unit cell.

12. A battery pack comprising the battery module of claim 11 .

13. The battery pack of claim 12 , wherein the battery pack is used as a power source of a medium and large sized device.

14. The battery pack of claim 13 , wherein the medium and large sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

15. A method of preparing the positive electrode active material for a secondary battery of claim 1 , the method comprising:

mixing first lithium cobalt oxide particles having an average particle diameter of 2 μm or less and second lithium cobalt oxide particles having an average particle diameter of 6 μm or more, and performing a heat treatment at a temperature of 600° C. or more,

wherein the first lithium cobalt oxide particles; or both of the first lithium cobalt oxide particles and the second lithium cobalt oxide particles are surface-treated with a metal-containing raw material so as to form said lithium metal oxide, and

wherein the metal-containing raw material includes a metal comprising at least one element selected from the group consisting of aluminum (Al), magnesium (Mg), tungsten (W), molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), iron (Fe), vanadium (V), chromium (Cr), barium (Ba), calcium (Ca), and niobium (Nb).