Anode active material, method of manufacturing the same, and lithium battery using the same

1. An anode active material comprising:

a first material comprising a plurality of complex material particles comprising silicon and graphite;

a second material comprising a carbon layer covering at least a portion of a surface of the first material; and

a third material comprising a silicon-metal alloy, the third material being formed between the first material and the second material.

2. The anode active material of claim 1 , wherein the weight ratio of silicon to graphite in the first material is about 2.0 or less.

3. The anode active material of claim 1 , wherein the weight ratio of silicon to graphite in the first material is about 1.5 or less.

4. The anode active material of claim 1 , wherein the weight ratio of silicon to graphite in the first material ranges from about 0.5 to about 1.4.

5. The anode active material of claim 1 , wherein the molar ratio of metal to silicon in the silicon-metal alloy is about 0.01 or greater.

6. The anode active material of claim 1 , wherein the molar ratio of metal to silicon in the silicon-metal alloy ranges from about 0.1 to about 0.5.

7. The anode active material of claim 1 , wherein the carbon layer is an amorphous carbon layer.

8. The anode active material of claim 1 , wherein carbon layer is present in an amount ranging from about 1 to about 20 wt % based on the total weight of the anode active material.

9. The anode active material of claim 1 , wherein carbon layer is present in an amount ranging from about 3 to about 15 wt % based on the total weight of the anode active material.

10. The anode active material of claim 1 , wherein the metal of the silicon-metal alloy is selected from the group consisting of nickel, cobalt, copper, zinc, aluminum and magnesium.

11. The anode active material of claim 1 , wherein the silicon-metal alloy is a silicon-nickel alloy.

12. The anode active material of claim 1 , wherein the carbon layer covers the entire surface of the first material.

13. A lithium battery comprising:

a cathode;

an anode comprising the anode active material according to claim 1 ; and

a separator.

14. A method of preparing an anode active material, the method comprising:

providing a mixture of silicon particles and graphite particles and milling the mixture;

adding to the mixture a salt selected from the group consisting of long-chain metal carboxylate salts and long-chain metal sulfonate salts; and

heat-treating the mixture in an environment selected from the group consisting of a vacuum and an inert gas atmosphere.

15. The method of claim 14 , wherein the salt comprises 20 or more carbon atoms and the metal is selected from the group consisting of nickel, cobalt, copper, zinc, aluminum and magnesium.

16. The method of claim 14 , wherein the salt is selected from the group consisting of nickel stearate, nickel oleate, nickel palmitate, nickel linoleate, nickel laurate, nickel myristate, copper stearate, copper oleate, copper palmitate, copper linoleate, copper laurate and copper myristate.

17. The method of claim 14 , wherein milling the mixture comprises high energy ball milling.

18. The method of claim 14 , wherein the heat-treatment is performed at a temperature ranging from about 500 to about 1200° C. for a period of time ranging from about 0.5 to about 5 hours.

19. The method of claim 14 , wherein an average particle diameter of the silicon particles ranges from about 0.05 to about 1 μm.

20. The method of claim 14 , wherein an average particle diameter of the graphite particles ranges from about 1 to about 20 μm.