Anode active material for lithium secondary battery, preparation method thereof, and lithium secondary battery comprising the same

1. An anode active material comprising:

carbon-based particles;

silicon nanowires grown on the carbon-based particles; and

a carbon coating layer formed on surfaces of the carbon-based particles and the silicon nanowires,

wherein a thickness of the carbon coating layer is in a range of 5 nm to 20 nm, and

the carbon coating layer covers the entire surfaces of the carbon-based particles and the silicon nanowires.

2. The anode active material of claim 1 , wherein the carbon-based particles comprises any one selected from the group consisting of carbon-based powder, carbon black, natural graphite, artificial graphite, and a mixture of two or more thereof.

3. The anode active material of claim 1 , wherein an average particle diameter of the carbon-based particles is in a range of 10 μm to 30 μm,

wherein the average particle diameter of the carbon-based particles is a particle diameter at 50% in a cumulative particle diameter distribution.

4. The anode active material of claim 1 , wherein a specific surface area of the carbon-based particles is in a range of 2.0 m 2 /g to 5.0 m 2 /g, and a compressed density of the carbon-based particles is in a range of 1.5 g/cc to 1.85 g/cc under a pressure of 12 MPa to 16 MPa,

wherein the specific surface area of the carbon-based particles is measured by a Brunauer-Emmett-Teller (BET) method.

5. The anode active material of claim 1 , wherein the silicon nanowire has a diameter ranging from 10 nm to 100 nm and a length ranging from 100 nm to 5 μm.

6. The anode active material of claim 1 , wherein an amount of silicon is in a range of 5 wt % to 30 wt % based on a total weight of the carbon-based particles and the silicon nanowires grown on the carbon-based particles.

7. An anode comprising a current collector, and the anode active material of claim 1 formed at least one surface of the current collector.

8. A lithium secondary battery comprising a cathode, the anode of claim 7 , and a separator disposed between the cathode and the anode.

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

growing silicon nanowires on carbon-based particles by using a silicon raw material and a catalytic metal; and

forming a carbon coating layer on surfaces of the silicon nanowires and the carbon-based particles on which the silicon nanowires are grown,

wherein a thickness of the carbon coating layer is in a range of 5 nm to 20 nm,

wherein the carbon coating layer is formed by coating the carbon-based particles on which the silicon nanowires are grown with a carbon precursor and performing a heat treatment,

wherein the carbon precursor comprises gas or amorphous carbon, and the gas includes carbon, and

wherein the amorphous carbon is a coal-derived pitch or a petroleum-derived pitch, and the coal-derived pitch and the petroleum-derived pitch have a weight-average molecular weight ranging from 500 to 800.

10. The method of claim 9 , wherein the growing of the silicon nanowires is performed by a method selected from the group consisting of a vapor-liquid-solid (VLS) method, a solid-liquid-solid (SLS) method, a metal organic chemical vapor deposition (MOCVD) method, and a molecular beam epitaxy (MBE) method.

11. The method of claim 9 , wherein the silicon raw material comprises SiCl 4 , SiH 4 , or a mixture thereof.

12. The method of claim 9 , wherein the catalytic metal comprises any one selected from the group consisting of gold (Au), iron (Fe), silver (Ag), nickel (Ni), and a mixed metal of two or more thereof.

13. The method of claim 9 , wherein a mixing ratio of the carbon-based particles and the silicon nanowires grown on the carbon-based particles to the carbon precursor is in a range of 90 parts by weight:10 parts by weight to 99 parts by weight:1 part by weight.

14. The method of claim 9 , wherein the heat treatment is performed at a temperature ranging from 300° C. to 1,500° C.

15. The method of claim 9 , wherein the coating is performed by a dry or wet coating method using an amorphous carbon precursor, or a chemical vapor deposition (CVD) method using the gas.

16. The method of claim 15 , wherein the wet coating method is performed by dipping the carbon-based particles on which the silicon nanowires are grown in an organic solvent in which the amorphous carbon that is prepared from the amorphous carbon precursor is diluted.

17. The method of claim 16 , wherein the organic solvent comprises any one selected from the group consisting of ethanol, toluene, methanol, hexane, acetone, tetrahydrofuran, pyridine, quinoline, benzoquinone, and a mixture of two or more thereof.