Negative active material for rechargeable lithium battery and rechargeable lithium battery including the same
A negative active material for a rechargeable lithium battery and a rechargeable lithium battery including the same, the negative active material including a Si-carbon composite that includes Si nanoparticles and an amorphous carbon, wherein the negative active material has a sphericity of 0.7 or more, and a BET specific surface area of 10 m 2 /g or less.
1. A negative active material for a rechargeable lithium battery, the negative active material comprising a Si-carbon composite that includes Si nanoparticles and an amorphous carbon,
wherein the negative active material has:
a sphericity of 0.7 or more, and
a BET specific surface area of 2.7 m 2 /g to 7.1 m 2 /g.
2. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the Si nanoparticles have a spherical shape.
3. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the Si-carbon composite includes secondary particles that are agglomerated Si nanoparticles.
4. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the amorphous carbon covers a surface of the Si nanoparticles.
5. The negative active material for a rechargeable lithium battery as claimed in claim 3 , wherein the amorphous carbon covers a surface of the secondary particles.
6. The negative active material for a rechargeable lithium battery as claimed in claim 3 , wherein the amorphous carbon fills pores between the Si nanoparticles.
7. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the Si nanoparticles are a flake type.
8. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the Si nanoparticles have a D50 average particle diameter of about 10 nm to about 200 nm.
9. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein a full width at half maximum, FWHM (111) of a diffraction peak at a (111) plane found by X-ray diffraction of the Si nanoparticles using a CuKα ray is about 0.3 degrees)(°) to about 7 degrees)(°).
10. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the negative active material has a particle diameter of about 40 μm or less.
11. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein a mixing ratio of the Si nanoparticles and the amorphous carbon is about 8:2 to about 2:8 by weight.
12. A rechargeable lithium battery, comprising:
a negative electrode comprising the negative active material as claimed in claim 1 ;
a positive electrode; and
an electrolyte.
13. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the negative active material is prepared by:
preparing silicon particles;
dispersing the silicon particles in a solvent;
spray drying the dispersed silicon particles in the solvent to form secondary particles;
mixing the secondary particles with an amorphous carbon precursor to form a mixture;
compression forming the mixture to form a compress-formation product;
heat treating the compress-formation product to form the negative active material.