초록

Disclosed is a negative active material for a rechargeable lithium battery that includes graphite particles, silicon micro-particles attached on the graphite particles and a carbon film partially or totally coated on the graphite particles.

대표청구항 ▼

1. A negative active material for a rechargeable lithium battery comprising: at least one graphite particle; at least one silicon micro-particle attached on a surface of the graphite particle; and an amorphous carbon film coated on the graphite particle and the silicon micro-particle. 2. The

1. A negative active material for a rechargeable lithium battery comprising: at least one graphite particle; at least one silicon micro-particle attached on a surface of the graphite particle; and an amorphous carbon film coated on the graphite particle and the silicon micro-particle. 2. The negative active material according to claim 1, wherein the silicon micro-particle is firmly attached on the surface of the graphite particle. 3. The negative active material according to claim 1, wherein the carbon film is a reaction-preventing layer for preventing a reaction between the graphite particle and an electrolyte. 4. The negative active material according to claim 1, wherein in the carbon film partially or totally coats the graphite particle to firmly attach the silicon micro-particle on the graphite particle. 5. The negative active material according to claim 1, wherein the carbon film is prepared by coating a polymer material on the graphite particle and calcinating the resulting material. 6. The negative active material according to claim 5, wherein the polymer material is at least one selected from a group consisting of vinyl resin, cellulose resin, phenol resin, pitch resin, and tar resin. 7. A negative active material for a rechargeable lithium battery comprising: at least one graphite particle; at least one silicon micro-particle attached on a surface of the graphite particle; and a carbon film coated on the graphite particle and the silicon micro-particle, wherein the content of the at least one silicon micro-particle is from 3 to 10 percent by weight, based on the total weight of the negative active material. 8. A negative active material comprising: a core comprising one or more graphite particles and one or more silicon micro-particles; and an amorphous carbon film coated on the core. 9. The negative active material according to claim 8, wherein the one or more silicon micro-particles are firmly attached on the surface of the one or more graphite particles. 10. The negative active material according to claim 8, wherein the carbon film is a reaction-protecting layer for preventing the reaction between the graphite particle and an electrolyte. 11. The negative active material according to claim 8, wherein the carbon partially or totally coats the graphite particle, and fixes the one or more silicon micro-particles on the surface of the one or more graphite particles. 12. The negative active material according to claim 8, wherein the carbon film is formed by coating a polymer material to the one or more graphite particles and calcinating the resulting material. 13. The negative active material according to claim 12, wherein the polymer material is at least one selected from a group consisting of vinyl resin, cellulose resin, phenol resin, pitch resin, and tar resin. 14. A negative active material comprising: a core comprising one or more graphite particles and silicon micro-particles; and a carbon film coated on the core, wherein the content of one or more silicon micro-particles is from 3 to 10 percent by weight. 15. A method of preparing a negative active material comprising: attaching a silicon micro-particle to a graphite particle; coating a polymer film on the graphite particle to prepare a negative active material precursor; and calcinating the negative active material precursor such that the polymer film is carbonized to obtain a carbon film. 16. The method of preparing the negative active material according to claim 15, wherein the calcination step is performed at a temperature between carbonization temperature of the polymer film and 1400° C.