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, the negative active material including secondary particles of agglomerated primary particles, the primary particles including Si particles with SiC on a surface of the Si particles; and an amorphous carbon surrounding the secondary particles, wherein a peak intensity ratio (I Si(111) /I SiC(111) ) of a peak intensity (I Si(111) )) at a Si (111) plane relative to a peak intensity (I SiC(111) ) at a SiC (111) plane is about 5 to about 50 measured by X-ray diffraction analysis using a CuKα ray.
1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising:
a physical mixture of a first negative active material and a crystalline carbon as a second active material, the crystalline carbon including graphite,
wherein the first negative active material comprises secondary particles of agglomerated primary particles, the primary particles including Si particles with SiC on a surface of the Si particles; and
an amorphous carbon surrounding the secondary particles,
wherein the first negative active material has:
a peak intensity ratio (I Si(111) / ISiC(111 ) of a peak intensity (I Si(111) ) at a Si (111) plane relative to a peak intensity (I ISiC(111 ) at a SiC (111) plane of about 5 to about 20 measured by X-ray diffraction analysis using a CuKα ray,
wherein the crystalline carbon material has a peak intensity ratio (I Gri(002) /I SiC(111) ) of a peak intensity (I Gr(002) ) at a crystalline carbon (002) plane relative to a peak intensity (II SiC(111) ) at a SiC (111) plane, measured by X-ray diffraction analysis using a CuKα ray of about 150 to about 1,500 in the negative electrode,
wherein a thickness of the SiC on the surface of the Si is about 5 nm or less,
wherein the negative active material includes:
about 5 wt % to about 20 wt % of SiC,
about 40 wt % to about 70 wt % of silicon, and
27 wt % to about 50 wt % of the amorphous carbon, all wt % being based on 100 wt % of the entire negative active material, and
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 particles using a CuKα ray is about 0.5 degrees (°) to about 7 degrees (°).
2. The negative active material for a rechargeable lithium battery as claimed in claim 1 , wherein the amorphous carbon fills pores between the primary particles.
3. The negative electrode for a rechargeable lithium battery as claimed in claim 1 , wherein:
the SiC is continuously on the surface of the Si particles in a form of a layer, or
the SiC is discontinuously on the surface of the Si particles in a form of a dot.
4. The negative electrode for a rechargeable lithium battery as claimed in claim 1 , wherein the Si particles are of a flake type.
5. The negative electrode for a rechargeable lithium battery as claimed in claim 1 , wherein the Si particles have an aspect ratio of about 5 to about 20.
6. The negative electrode for a rechargeable lithium battery as claimed in claim 1 , wherein the Si particles have a particle diameter of about 10 nm to 200 nm.
7. A rechargeable lithium battery, comprising:
the negative electrode as claimed in claim 1 ;
a positive electrode; and
an electrolyte.
8. The negative electrode for a rechargeable lithium battery as claimed in claim 1 , wherein the first negative active material includes:
about 5 wt % to about 20 wt % of SiC,
about 40 wt % to about 60 wt % of silicon, and
35 wt % to about 50 wt % of the amorphous carbon, all wt % being based on 100 wt % of the entire negative active material.