Positive active material, positive electrode and lithium battery including the positive active material, and method of manufacturing the positive active material

1. A positive active material comprising:

a positive active material core particle for intercalating and deintercalating lithium ions; and

a coating layer at least partially surrounding the positive active material core particle and comprising a ceramic composite represented by Formula 1:

Li 7+a La 3−b Zr 2−c M d O 12+e   Formula 1

wherein M comprises at least one selected from aluminum (Al), titanium (Ti), scandium (Sc), vanadium (V), yttrium (Y), niobium (Nb), hafnium (Hf), tantalum (Ta), silicon (Si), gallium (Ga), and germanium (Ge), and

−1≦a≦1, 0≦b≦2, 0≦c≦2, 0<d≦2, and 0≦e≦1.

2. The positive active material of claim 1 , wherein the ceramic composite is represented by Formula 2:

Li 7+a′ La 3−b′ Zr 2−c′ M d′ O 12+e′   Formula 2

wherein M comprises at least one selected from Al, Ti, Sc, V, Y, Nb, Hf, Ta, Si, Ga, and Ge, and

−0.5≦a′≦0.5, 0≦b′≦1, 0≦c′≦1, 0≦d′≦1, and 0≦e′≦0.5.

3. The positive active material of claim 1 , wherein the ceramic composite is represented by Formula 3:

Li 7 La 3−b″ Zr 2 Al d″ O 12   Formula 3

wherein 0<b″≦2 and 0<d″≦2.

4. The positive active material of claim 1 , wherein the ceramic composite is represented by Formula 4:

Li 7 La 3 Zr 2−c′″ Ti d′″ O 12   Formula 4

wherein 0<c′″<2 and 0<d′″<2.

5. The positive active material of claim 1 , wherein the ceramic composite is represented by Formula 5:

Li 7 La 3−x Al x Zr 2−y Ti y O 12   Formula 5

wherein 0≦x≦2, 0≦y≦2, and 0<x+y≦2.

6. The positive active material of claim 1 , wherein the coating layer is discontinuous.

7. The positive active material of claim 1 , wherein the coating layer comprises coating particles comprising the ceramic composite.

8. The positive active material of claim 7 , wherein the coating particles have an average particle diameter in a range of about 100 nm to about 1,000 nm.

9. The positive active material of claim 1 , wherein the coating layer has a thickness in a range of about 100 nm to about 1,000 nm.

10. The positive active material of claim 1 , wherein the positive active material core particle comprises at least one selected from LiCoO 2 ; LiNiO; LiMnO 2 ; LiMn 2 O 4 ; Li(Ni a Co b Mn c )O 2 , wherein 0<a<1, 0<b<1, 0<c<1, a+b+c=1; LiNi 1−y Co y O 2 , wherein 0≦y<1; LiCo 1−y Mn y O 2 , wherein 0≦y<1; LiNi 1−y Mn y O 2 , wherein 0≦y<1; LiMn 2−z Ni z O 4 , wherein 0<z<2; LiMn 2−z Co z O 4 , wherein 0<z<2; V 2 O 5 ; TiS; and MoS.

11. The positive active material of claim 1 , wherein the positive active material has an operating potential in a range of about 4.0 V to about 5.5 V.

12. The positive active material of claim 1 , wherein the positive active material core particle has an average particle diameter in a range of about 1 μm to about 30 μm.

13. The positive active material of claim 1 , wherein the coating layer is present in the positive active material at a mole ratio in a range of about 0.05 to about 5 mol % based on 1 mole of the positive active material core particle.

14. A lithium battery comprising the positive active material of claim 1 .

15. A method of manufacturing a positive active material according to claime 1 , the method comprising:

preparing a mixed solution comprising a lanthanum (La) precursor, a zirconium (Zr) precursor, and an additive metal M, wherein M comprises at least one selected from Al, Ti, Sc, V, Y, Nb, Hf, Ta, Si, Ga, and Ge;

adding a weak acid comprising citric acid, lactic acid, acetic acid, formic acid, oxalic acid, uric acid, or a mixture thereof, to the mixed solution to prepare a coating solution;

applying a coating of the coating solution onto a surface of a positive active material core particle capable of intercalating and deintercalating lithium ions; and

heat-treating the coating to prepare the positive active material.

16. The method of claim 15 , wherein the positive active material core particle capable of intercalating and deintercalating lithium ions comprises a lithium transition metal oxide.

17. The method of claim 15 , wherein the coating solution further comprises a dispersing agent comprising isopropyl alcohol (IPA), n-butyl alcohol, terpineol, sodium hexametaphosphate, or a mixture thereof.

18. The method of claim 15 , wherein the coating solution further comprises a solvent, and the method further comprises evaporating the solvent from the coating solution before the applying of the coating of the coating solution onto the surface of the positive active material core particle capable of intercalating and deintercalating lithium ions.

19. The method of claim 15 , further comprising drying the coating of the coating solution at a temperature in a range of about 100° C. to about 300° C. between the applying of the coating of the coating solution onto the surface of the positive active material core particle capable of intercalating and deintercalating lithium ions and the heat-treating.

20. The method of claim 15 , wherein the heat-treating is performed at a temperature in a range of about 600° C. to about 1,000° C.