Positive electrode active material comprising an agglomeration of at least two primary particles for lithium battery and lithium battery using the same

1. A positive active material for a lithium battery, comprising:

at least one secondary particle comprising an agglomeration of at least two primary particles, wherein the primary particles comprise a lithium composite oxide; and

an amorphous lithium salt.

2. The positive active material according to claim 1 , wherein the amorphous lithium salt is between adjacent primary particles.

3. The positive active material according to claim 2 , wherein the amorphous lithium salt is present at least at a grain boundary between adjacent primary particles.

4. The positive active material according to claim 1 , wherein the amorphous lithium salt is a lithium carbonate, a lithium sulfate, a lithium nitrate, or a lithium hydroxide.

5. The positive active material according to claim 1 , wherein the amorphous lithium salt is present in an amount of about 0.01 to about 10 parts by weight based on 100 parts by weight of the lithium composite oxide.

6. The positive active material according to claim 1 , wherein the amorphous lithium salt is present in an amount of about 0.01 to about 10 parts by weight based on 100 parts by weight of the lithium composite oxide.

7. The positive active material according to claim 1 , wherein the amorphous lithium salt is present in an amount of about 0.1 to about 2 parts by weight based on 100 parts by weight of the lithium composite oxide.

8. The positive active material according to claim 1 , wherein the primary particles have an average particle size of about 1 to about 3 μm.

9. The positive active material according to claim 1 , wherein the secondary particles have an average particle size of about 10 to about 15 μm.

10. The positive active material of claim 1 , wherein the lithium composite oxide comprises a compound represented by Formula 1:

Li a (Ni x Co y Me z ) 2-a O 2   Formula 1

wherein 0.5≦x≦1, 0≦y≦0.5, 0<z≦0.5, 0.90<a≦1.15, and Me is selected from the group consisting of Al, Mn, Ti and Ca.

11. The positive active material according to claim 10 , wherein 0.5≦x≦0.6, 0.2≦z≦0.3, 0.90≦a≦1.0.

12. The positive active material according to claim 10 , wherein the lithium composite oxide is LiNi 0.5 Co 0.2 Mn 0.3 O 2 or LiNi 0.6 Co 0.2 Mn 0.2 O 2 .

13. A method of manufacturing the positive active material of claim 1 , the method comprising:

mixing the lithium composite oxide and the amorphous lithium salt to form a mixture; and

heat treating the mixture at a temperature of from greater than about 700° C. to about 950° C.

14. The method according to claim 13 , wherein the lithium composite oxide comprises a compound represented by Formula 1:

Li x Ni 1-x-y Co y Me z O 2   Formula 1

wherein 0.5≦x≦1, 0≦y≦0.5, 0<z≦0.5, 0.90<a≦1.15, and Me is selected from the group consisting of Al, Mn, Ti and Ca.

15. The method according to claim 13 , wherein the heat treating the mixture comprises heating the mixture at a temperature of about 750° C. to about 900° C.

16. The method according to claim 13 , wherein the heat treating the mixture comprises heating the mixture at a temperature of about 800° C. to about 900° C.

17. A positive electrode, comprising a positive active material comprising:

at least one secondary particle comprising an agglomeration of at least two primary particles, wherein the primary particles comprise a lithium composite oxide; and

an amorphous lithium salt.

18. A lithium battery, comprising:

a positive electrode comprising a positive active material comprising:

at least one secondary particle comprising an agglomeration of at least two primary particles, wherein the primary particles comprise a lithium composite oxide; and

an amorphous lithium salt;

a negative electrode comprising a negative active material; and

an electrolyte.