Composite anode active material, method of preparing the same, and anode and lithium secondary battery including the composite anode active material

1. A composite anode active material comprising:

a silicon material; and

a coating layer formed on at least a portion of a surface of the silicon material,

wherein the coating layer is chemically bonded to the silicon material,

wherein the coating layer comprises a hydrosilylation product of a C4-C30 alkene comprising a terminal —C(═O)OR group, wherein R is a hydrogen, a C1-C5 alkyl group, a C2-C6 heteroalkyl group, a C6-C12 aryl group, or a C7-C13 arylalkyl group, each of which except hydrogen is substituted or unsubstituted, and

wherein the coating layer further comprises a polymer that has been chemically reacted with the —C(═O)OR group of the hydrosilylation product.

2. The composite anode active material of claim 1 , wherein the polymer before reacting comprises a hydroxyl group (—OH) capable of reacting with the —C(═O)OR group of the hydrosilylation product.

3. The composite anode active material of claim 1 , wherein the hydrosilylation product of the C4-C30 alkene is a hydrosilylation product of a hydride-terminated silicon material and the C4-C30 alkene.

4. The composite anode active material of claim 1 , wherein the C4-C30 alkene comprising the terminal —C(═O)OR group is a compound represented by Formula 1:

wherein, in Formula 1,

n is an integer of 1 to 10, and

R 1 , R 2 , and R are each independently a hydrogen, a C1-C5 alkyl group a C2-C6 heteroalkyl group, a C6-C12 aryl group, or a C7-C13 arylalkyl group, each of which is substituted or unsubstituted.

5. The composite anode active material of claim 4 , wherein the compound represented by Formula 1 is a compound represented by Formula 2:

wherein, in Formula 2,

n is an integer of 1 to 10, and

R is a hydrogen, a methyl group, or an ethyl group.

6. The composite anode active material of claim 4 , wherein the compound represented by Formula 1 is one of compounds represented by Formulae 3 to 5, 10-undecenoic acid, methyl 10-undecenoate, ethyl 10-undecenoate, 4-pentenoic acid, methyl 4-pentenate, ethyl 4-pentenate, 2-Methyl-4-pentenoic acid, 3-Methyl-4-pentenoic acid, 2,2-dimethyl-4-pentenoic acid, 8-nonenoic acid, methyl 8-nonenoate, and ethyl 8-nonenoate:

7. The composite anode active material of claim 1 , wherein the polymer is at least one selected from a polyvinylalcohol, a polyvinylacetate, and a cellulose ether.

8. The composite anode active material of claim 1 , wherein the silicon material is at least one selected from silicon (Si), SiO x (wherein 0<x<2), and a silicon alloy.

9. The composite anode active material of claim 1 , wherein an amount of the C4-C30 alkene comprising the terminal —C(═O)OR group is in a range of about 0.01 part to about 50 parts by weight based on 100 parts by weight of the silicon material.

10. The composite anode active material of claim wherein an amount of the polymer is in a range of about 0.01 part to about 50 parts by weight of the silicon material.

11. The composite anode active material of claim 1 , wherein the coating layer comprises a unit represented by Formula 6:

wherein, in Formula 6,

n is an integer of 1 to 10, and

R is a hydrogen, a methyl group, or an ethyl group, and

* refers to a binding site to a surface of the silicon material.

12. The composite anode active material of claim 1 , wherein the coating layer comprises a unit represented by Formula 7:

wherein, in Formula 7,

n is an integer of 1 to 10,

m is an integer of 5 to 18,000, and

* is a binding site to a surface of the silicon material.

13. The composite anode active material of claim 1 further comprising a carbon material.

14. A method of preparing the composite anode active material of claim 1 , the method comprising:

obtaining a hydride-terminated silicon material by etching the silicon material;

reacting the hydride-terminated silicon material with a C4-C30 alkene comprising a terminal —C(═O)OR group to obtain a hydrosilylation product comprising a terminal —C(═O)OR group, wherein R is a hydrogen, a C1-C5 alkyl group, a C2-C6 heteroalkyl group, a C6-C12 aryl group, or a C7-C13 arylalkyl group, each of which except hydrogen is substituted or unsubstituted to obtain the composite anode active material, and

reacting a polymer comprising a functional group capable of reacting with the terminal —C(═O)OR group of the hydrosilylation product to obtain the composite anode active material.

15. The method of claim 14 , further comprising

mixing the silicon material and a carbon material to obtain a mixture; and

milling the mixture before the obtaining of the hydride-terminated silicon material.

16. An anode comprising a composite anode active material, wherein the composite anode active material comprises:

a silicon material; and

a coating layer formed on at least a portion of a surface of the silicon material,

wherein the coating layer is chemically bonded to the silicon material,

wherein the coating layer comprises a hydrosilylation product of a C4-C30 alkene comprising a terminal —C(═O)OR group, wherein R is a hydrogen, a C1-C5 alkyl group, a C2-C6 heteroalkyl group, a C6-C12 aryl group, or a C7-C13 arylalkyl group, each of which except hydrogen is substituted or unsubstituted, and

wherein the coating layer further comprises a polymer that has been chemically reacted with the —C(═O)OR group of the hydrosilylation product.

17. A lithium secondary battery comprising the anode of claim 16 .