COMPOSITE PARTICLES, METHOD FOR PRODUCING THE SAME, AND USES THEREOF
An object of the present invention is to provide carbon-coated Si—C composite particles capable of maintaining a high Si utilization rate and suppressing deterioration of initial coulombic efficiency due to oxidation over time of a lithium-ion secondary battery. The carbon-coated Si—C composite particles of the present invention includes Si—C composite particles containing a carbon material and silicon; and a carbonaceous layer present on surfaces of the Si—C composite particles, wherein the carbon coverage thereof is 70% or more, wherein the BET specific surface area is 200 m 2 /g or less; wherein R value (I D /I G ) is 0.30 or more and 1.10 or less and I Si /I G is 0.15 or less, when the peak attributed to Si is present at 450 to 495 cm −1 and the intensity of the peak is defined as I Si , in Raman spectrum of the carbon-coated Si—C composite particles: and wherein the full width at half maximum of the peak of a 111 plane of Si is 3.00 deg. or more, and (peak intensity of a 111 plane of SiC)/(peak intensity of the 111 plane of Si) is 0.01 or less, in the XRD pattern measured by powder XRD using a Cu-Kα ray of the carbon-coated Si—C composite particles.
1 . Carbon-coated Si—C composite particles comprising:
Si—C composite particles containing a carbon material and silicon; and
a carbonaceous layer present on surfaces of the Si—C composite particles,
wherein a coverage (carbon coverage) by the carbonaceous layer on the surfaces of the Si—C composite particles is 70% or more,
wherein a BET specific surface area is 200 m 2 /g or less;
wherein R value (I D /I G ) is 0.30 or more and 1.10 or less, and I Si /I G ) is 0.15 or less when a peak attributed to Si is present at 450 to 495 cm −1 and an intensity of the peak is defined as I Si , in a Raman spectrum of the carbon-coated Si—C composite particles; and
wherein a full width at half maximum of a peak of a 111 plane of Si is 3.00 deg. or more, and (peak intensity of a 111 plane of SiC)/(peak intensity of the 111 plane of Si) is 0.01 or less, in a XRD pattern measured by powder XRD using a Cu-Kα ray of the carbon-coated Si—C composite particles.
2 . The carbon-coated Si—C composite particles according to claim 1 , wherein a true density as measured by a He pycnometer is 2.00 to 2.20 g/cm 3 .
3 . The carbon-coated Si—C composite particles according to claim 1 , wherein a 50% particle size D V50 in a volume-based cumulative particle size distribution is 2.0 to 30.0 μm.
4 . The carbon-coated Si—C composite particles according to claim 1 , wherein a content of silicon is 20 to 70% by mass.
5 . The carbon-coated Si—C composite particles according to claim 1 , wherein an oxygen content is 10.0% by mass or less.
6 . The carbon-coated Si—C composite particles according to claim 1 , wherein an oxygen content is 4.0% by mass or less.
7 . The carbon-coated Si—C composite particles according to claim 1 , wherein the carbonaceous layer has an average thickness of 5 to 100 nm.
8 . The carbon-coated Si—C composite particles according to claim 1 , wherein R value (I D /I G ) is 0.30 or more and less than 1.00.
9 . The carbon-coated Si—C composite particles according to claim 1 , wherein a BET specific surface area is 6.0 m 2 /g or less.
10 . The carbon-coated Si—C composite particles according to claim 1 , wherein a BET specific surface area is 5.0 to 200.0 m 2 /g.
11 . A polymer-coated carbon-coated Si—C composite particles comprising:
a polymer coating layer on at least a part of the surfaces of the carbon-coated Si—C composite particles according to claim 1 ,
wherein the polymer coating layer comprises inorganic particles comprising one or more selected from graphite and carbon black and a polymer, and a polymer content is 0.1 to 10.0% by mass.
12 . A method for producing carbon-coated Si—C composite particles comprising:
a step (A) of allowing a silicon-containing gas to act on porous carbon to precipitate silicon in pores and on a surface of the porous carbon to obtain Si—C composite particles; and
a step (B) of forming a carbonaceous layer on surfaces of the Si—C composite particles by a chemical vapor deposition (CVD) method at 600 to 750° C. using at least one selected from acetylene and ethylene as a carbon source.
13 . The method for producing carbon-coated Si—C composite particles according to claim 12 , wherein the step (A) and the step (B) are continuously performed.
14 . The method for producing carbon-coated Si—C composite particles according to claim 12 or 13 , wherein the carbon-coated Si—C composite particles according to claim 1 .
15 . A negative electrode mixture layer comprising the carbon-coated Si—C composite particles according to claim 1 .
16 . A negative electrode mixture layer comprising the polymer-coated carbon-coated Si—C composite particles according to claim 11 .
17 . A lithium-ion secondary battery comprising the negative electrode mixture layer according to claim 15 .
18 . A lithium-ion secondary battery comprising the negative electrode mixture layer according to claim 16 .