Composite, method of preparing the same, electrode including the composite, and lithium battery including the electrode

1. A composite comprising:

a carbonaceous material;

a plurality of silicon structures disposed on the carbonaceous material; and

a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures,

wherein a silicon structure of the plurality of silicon structures comprises

silicon, and

a silicon oxide of the formula SiO x which is disposed on a surface of the silicon, wherein 0<x<2.

2. The composite of claim 1 , wherein the graphene layer is disposed between the silicon oxide and the carbonaceous material, and

wherein the graphene layer anchors the silicon structure of the plurality of silicon structures to the carbonaceous material.

3. The composite of claim 1 , wherein the silicon structures of the plurality of silicon structures are connected by the graphene layer.

4. The composite of claim 1 , wherein the carbonaceous material comprises at least one selected from a graphite fiber textile, carbon nanotube, carbon nanotube bundle, and carbon fiber.

5. The composite of claim 1 , wherein the carbonaceous material and the plurality of silicon structures, which are disposed on the carbonaceous material, form a twist aligned carbon nanotube-silicon structure.

6. The composite of claim 1 ,

wherein the carbonaceous material comprises carbon nanotubes,

wherein the plurality of silicon structures are disposed on the carbon nanotubes, and

wherein the graphene layer is disposed on the plurality of silicon structures.

7. The composite of claim 6 , wherein the carbon nanotubes, the silicon structures, and the graphene layer are the form of a bundle.

8. The composite of claim 1 ,

wherein an amount of the plurality of silicon structures is about 1 part to about 98 parts by weight, based on 100 parts by weight of the composite, and

wherein an amount of the graphene layer is in a range of about 1 part to about 30 parts by weight, based on 100 parts by weight of the composite.

9. The composite of claim 1 , wherein a thickness of the silicon oxide of the plurality of silicon structures is 300 micrometers or less.

10. The composite of claim 1 , wherein a 2D peak of graphene of the graphene layer is observed in a range of about 2600 cm −1 to about 2800 cm −1 , when the composite is analyzed by Raman spectroscopy.

11. The composite of claim 1 , wherein the graphene layer comprises 1 to 15 layers of graphene.

12. The composite of claim 1 , wherein the graphene extends to a distance of about 10 nanometers or less from the silicon of the silicon structure.

13. The composite of claim 12 , wherein the graphene extends to a distance of about 1 nanometer or less from the silicon of the silicon structure.

14. An electrode comprising:

a carbonaceous material;

a plurality of silicon structures disposed on the carbonaceous material; and

a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures,

wherein a silicon structure of the plurality of silicon structures comprises a composite comprising

silicon, and

a silicon oxide of the formula SiO x , wherein 0<x<2, disposed on a surface of the silicon.

15. The electrode of claim 14 , wherein the graphene extends to a distance of about 10 nanometers or less from the silicon of the silicon structure.

16. The electrode of claim 15 , wherein the graphene extends to a distance of about 1 nanometer or less from the silicon of the silicon structure.

17. A lithium battery comprising the electrode of claim 14 .

18. A method of preparing a composite, the method comprising:

disposing a composition comprising a plurality of silicon structures and a solvent on a carbonaceous material to form a coating, wherein a silicon structure of the plurality of silicon structures comprises

silicon, and

a silicon oxide of the formula SiO x which is disposed on a surface of the silicon, wherein 0<x<2;

drying the coating to obtain a precursor structure, which comprises the carbonaceous material and the plurality of silicon structures coated on the carbonaceous material;

contacting the precursor structure with a carbonaceous source gas; and

heat-treating carbonaceous source gas and the precursor structure to prepare the composite, wherein the composite comprises

a carbonaceous material,

a plurality of silicon structures disposed on the carbonaceous material; and

a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures, wherein a silicon structure of the plurality of silicon structures comprises silicon, and a silicon oxide of the formula SiO x which is disposed on a surface of the silicon, wherein 0<x<2.

19. The method of claim 18 , wherein the solvent comprises at least one selected from isopropyl alcohol, methanol, ethanol, butanol, and tetrahydrofuran.

20. The method of claim 18 , wherein the carbonaceous source gas comprises at least one selected from a compound represented by Formula 1, a compound represented by Formula 2, and an oxygen-containing gas represented by Formula 3:

C n H (2n+2−a) (OH) a   Formula 1

wherein, in Formula 1, n is an integer of 1 to 20, and a is an integer of 0 or 1,

C n H 2n   Formula 2

wherein, in Formula 2, n is an integer of 2 to 6, and

C x H y O z   Formula 3

wherein, in Formula 3, x is an integer of 0 or 1 to 20, y is an integer of 0 or 1 to 20, and z is an integer of 1 or 2.

21. The method of claim 20 , wherein the oxygen-containing gas is at least one selected from carbon dioxide, carbon monoxide, and water.

22. The method of claim 20 , wherein the carbonaceous source gas further comprises at least one inert gas selected from nitrogen, helium, and argon.

23. The method of claim 20 , wherein the compound represented by Formula 1 and the compound represented by Formula 2 are at least one selected from methane, ethylene, propylene, methanol, ethanol, and propanol.

24. The method of claim 20 , wherein the carbonaceous source gas is methane; a gas mixture comprising methane and an inert gas; an oxygen-containing gas; or a gas mixture comprising methane and an oxygen-containing gas.

25. The method of claim 24 , wherein the carbonaceous source gas is methane or a gas mixture of methane and carbon dioxide.

26. The method of claim 18 , wherein the heat-treating is performed at a temperature in a range of about 700° C. to about 1100° C.