Composite particles, negative electrode material, and lithium-ion secondary battery
An object of the present invention is to provide composite particles capable of suppressing oxidation over time of a Si—C composite material. Composite particles (B) of the present invention contains composite particles (A) containing carbon and silicon; and amorphous layers coating surfaces thereof, where the composite particles (B) have I Si /I G of 0.10 or more and 0.65 or less, and have R value (I D /I G ) of 1.00 or more and 1.30 or less, when a peak due to silicon is present at 450 to 495 cm −1 , an intensity of the peak is defined as I Si , an intensity of a G band (peak intensity in the vicinity of 1600 cm −1 ) is defined as I G , and an intensity of a D band (peak intensity in the vicinity of 1360 cm −1 ) is defined as I D in a Raman spectrum, and where the composite particles (B) have a full width at half maximum of a peak of a 111 plane of Si of 3.0 deg. or more using a Cu-Kα ray in an XRD pattern.
1 . Composite particles (B) comprising:
composite particles (A) containing carbon and silicon; and
amorphous layers coating surfaces thereof,
wherein the composite particles (B) have I Si /I G of 0.10 or more and 0.65 or less, and have R value (I D /I G ) of 1.00 or more and 1.30 or less,
when a peak due to silicon is present at 450 to 495 cm −1 , an intensity of the peak is defined as I Si , an intensity of a G band (peak intensity in the vicinity of 1600 cm −1 ) is defined as I G , and an intensity of a D band (peak intensity in the vicinity of 1360 cm −1 ) is defined as I D in a Raman spectrum, and
wherein the composite particles (B) have a full width at half maximum of a peak of a 111 plane of Si of 3.0 deg. or more using a Cu-Kα ray in an XRD pattern.
2 . The composite particles (B) according to claim 1 ,
wherein (peak intensity of a 111 plane of SiC)/(peak intensity of the 111 plane of Si) is 0.004 or less in the XRD pattern of the composite particles (B) using the Cu-Kα ray.
3 . The composite particles (B) according to claim 1 , wherein the amorphous layers coating the surfaces of the composite particles (A) are layers containing at least one selected from the group consisting of a metal oxide and carbon.
4 . The composite particles (B) according to claim 3 , wherein the metal oxide in the amorphous layers coating the surfaces of the composite particles (A) contains at least one selected from the group consisting of oxides of Al, Ti, V, Cr, Hf, Fe, Co, Mn, Ni, Y, Zr, Mo, Nb, La, Ce, Ta, and W and Li-containing oxides.
5 . The composite particles (B) according to claim 4 , wherein a content of the metal element is 0.1% by mass or more and 10.0% by mass or less.
6 . The composite particles (B) according to claim 3 , wherein the metal oxide in the amorphous layers coating the surfaces of the composite particles (A) is lithium titanate (Li 4 Ti 5 O 12 ), and a content of titanium in the composite particles (B) is 0.1% by mass or more and 10.0% by mass or less.
7 . The composite particles (B) according to claim 3 , wherein the metal oxide in the amorphous layers coating the surfaces of the composite particles (A) is niobium pentoxide (Nb 2 O 5 ) or oxygen-deficient niobium oxide (Nb 2 O x , x=4.5 to 4.9), and a content of niobium in the composite particles (B) is 0.1% by mass or more and 20.0% by mass or less.
8 . The composite particles (B) according to claim 3 , wherein the amorphous layers coating the surfaces of the composite particles (A) contains only carbon.
9 . The composite particles (B) according to claim 1 , wherein the amorphous layers coating the surfaces of the composite particles (A) have a thickness of 0.1 nm or more and 30 nm or less.
10 . The composite particles (B) according to claim 1 , wherein the amorphous layers coating the surfaces of the composite particles (A) have a coverage of 50% or more.
11 . The composite particles (B) according to claim 1 , wherein an oxygen content in the composite particles (B) is 10% by mass or less.
12 . The composite particles (B) according to claim 1 , wherein a content of silicon in the composite particles (B) is 20% by mass or more and 70% by mass or less.
13 . The composite particles (B) according to claim 1 , wherein the composite particles (B) have a D v50 of 1.0 μm or more and 30.0 μm or less and a BET specific surface area of 0.3 m 2 /g or more and 10.0 m 2 /g or less.
14 . The composite particles (B) according to claim 1 , wherein the composite particles (B) satisfy at least either of presence of two exothermic peaks at 400° C. to 800° C., and absence of exothermic peak at 700±10° C., in thermal analysis in an air atmosphere.
15 . The composite particles (B) according to claim 1 , wherein metal oxide particles having an average particle size of 100 nm or less are adhered to the surfaces of the composite particles (B).
16 . A method for producing the composite particles (B) according to claim 1 , wherein the surfaces of the composite particles (A) are coated with amorphous layers by a physical vapor deposition method (PVD).
17 . A method for producing the composite particles (B) according to claim 1 , wherein the surfaces of the composite particles (A) are coated with metal oxide layers by an atomic layer deposition method (ALD).
18 . A negative electrode material comprising the composite particles (B) according to claim 1 .
19 . A negative electrode mixture layer comprising the negative electrode material according to claim 18 .
20 . A lithium-ion secondary battery comprising the negative electrode mixture layer according to claim 19 .