COMPOSITE PARTICLES, METHOD FOR PRODUCING SAME AND USE OF SAME
The present invention provides composite particles consisting of a Si—C composite material capable of achieving a reduction in volume expansion of an electrode during charging in a lithium-ion rechargeable battery. The present invention includes composite particles including a carbon material and silicon, wherein a true density (He true density) by dry density measurement using helium gas is 1.30 g/cm 3 or more and 2.00 g/cm 3 or less, a true density (BA true density) by wet density measurement using 1-butanol is 1.00 g/cm 3 or more and 1.64 g/cm 3 or less, and the He true density is greater than the BA true density.
1 . Composite particles comprising a carbon material and silicon, wherein:
a He true density, which is the true density by dry density measurement using helium gas, is 1.30 g/cm 3 or more and 2.10 g/cm 3 or less,
a BA true density, which is the true density by wet density measurement using 1-butanol, is 1.00 g/cm 3 or more and 1.64 g/cm 3 or less, and
the He true density is greater than the BA true density.
2 . The composite particles according to claim 1 , further comprising cavities having a diameter of 0.2 μm or more and 20 μm or less as observed in a cross-section thereof.
3 . The composite particles according to claim 1 , wherein a peak exists in the Raman spectrum between 450 cm −1 and 495 cm −1 .
4 . The composite particles according to claim 3 , wherein the intensity of the peak is denoted I Si and the intensity of the G band (peak intensity close to 1,580 cm −1 ) is denoted I G , and I Si /I G is 1.3 or less.
5 . The composite particles according to claim 4 , wherein the intensity of the D band (peak intensity close to 1,350 cm −1 ) is denoted I D , and I D /I G is between 0.2 and 1.4.
6 . The composite particles according to claim 1 , wherein the carbon material is porous carbon, and silicon is present in the pores of the porous carbon.
7 . The composite particles according to claim 1 , wherein a silicon content is 30 mass % or more and 80 mass % or less, and an oxygen content is 4.0 mass % or less.
8 . The composite particles according to claim 1 , wherein (peak intensity of SiC (111) surface)/(peak intensity of Si (111) surface) is 0.01 or less in an XRD pattern by powder XRD using Cu-Kα radiation.
9 . The composite particles according to claim 1 , wherein the 50% particle diameter D V50 in the volume-based cumulative particle size distribution is between 1.0 m and 40.0 μm, and the 90% diameter D V90 is 50.0 μm or less.
10 . The composite particles according to claim 1 , wherein the BET specific surface area is 0.5 m 2 /g or more and 30.0 m 2 /g or less.
11 . The composite particles according to claim 1 , wherein the atomic ratios of Si, O, and C obtained from the narrow spectra of X-ray photoelectron spectroscopy are denoted A Si , A O , and A C , respectively, and the ratios of Si type from Si 2p spectrum analysis, SiO 2 and SiO are denoted B SiO2 and B SiO , respectively, A Si is 0.05 or more, and A C /(A C +A Si ×(B SiO2 +B SiO )) is 0.55 or more.
12 . A method for producing composite particles, the method comprising:
(A) contacting a gas including a silicon-containing gas with a porous carbon at 300° C. or more and 500° C. or less to precipitate silicon in pores of the porous carbon,
wherein:
the porous carbon includes cavities having a diameter of 0.2 μm or more and 20 μm or less as observed in a cross-section thereof; and
in a nitrogen gas absorption test performed on the porous carbon, when the pore volume when a relative pressure P/P 0 is 0.01 is denoted V 0.01 , and a pore volume when the relative pressure P/P 0 is 0.99 is denoted V 0.99 ,
V 0.99 is 0.4 cm 3 /g or more and 1.5 cm 3 /g or less, and
V 0.01 /V 0.99 is 0.4 or more.
13 . The method for producing composite particles according to claim 12 , further comprising:
(B) contacting a gas including a hydrocarbon having an unsaturated bond with the particles obtained in the contacting step (A) at 500° C. or lower.
14 . The method for producing composite particles according to claim 12 , further comprising:
(C) oxidizing the particles obtained in the contacting step (A).
15 . The method for producing composite particles according to claim 13 , further comprising:
(C) oxidizing the particles obtained in the contacting step (B).
16 . The method for producing composite particles according to claim 12 , wherein:
a He true density of the composite particles, which is the true density by dry density measurement using helium gas, is 1.30 g/cm 3 or more and 2.10 g/cm 3 or less,
a BA true density of the composite particles, which is the true density by wet density measurement using 1-butanol, is 1.00 g/cm 3 or more and 1.64 g/cm 3 or less, and
the He true density is greater than the BA true density.
17 . A negative electrode active material comprising the composite particles according to claim 1 .
18 . The negative electrode composite layer comprising the negative electrode active material according to claim 17 .
19 . A lithium-ion rechargeable battery comprising the negative electrode composite layer according to claim 18 .