Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery
A negative electrode material for a lithium ion secondary battery including carbon over a part or a whole of a surface of an oxide of silicon, in which the content of the carbon is from 0.5 mass-% to less than 5 mass-%.
1. A lithium ion secondary battery, comprising:
a positive electrode;
a negative electrode; and
an electrolyte,
wherein the negative electrode comprises:
a current collector; and
a negative electrode material layer provided on the current collector and comprising a negative electrode material (SiOx-C) and a carbonaceous electrode material (C),
wherein the negative electrode material (SiOx-C) comprises an oxide of silicon and silicon crystallites, and carbon over a part or a whole of a surface of the oxide of silicon, wherein the content of the carbon with respect to the whole negative electrode material (SiOx-C) is from 0.5 mass % to 4.5 mass %, wherein a crystallite size of the silicon crystallites is 2 nm or more and 8 nm or less, wherein the oxide of silicon is represented by a formula SiOx (x is 0<x≤2), and wherein a ratio of the negative electrode material (SiOx-C) to the carbonaceous negative electrode material (C) is from 0.1:99.9 to 20:80 in terms of mass.
2. The lithium ion secondary battery according to claim 1 , wherein the carbon included in the negative electrode material (SiOx-C) comprises low crystallinity carbon.
3. The lithium ion secondary battery according to claim 1 , wherein a diffraction peak assignable to Si (111) is observed when the negative electrode material (SiOx-C) is subjected to a powder X-ray diffraction (XRD) analysis.
4. The lithium ion secondary battery according to claim 1 , wherein the content of the carbon included in the negative electrode material (SiOx-C) with respect to the whole negative electrode material (SiOx-C) is from 0.5 mass % to 4.0 mass %.
5. The lithium ion secondary battery according to claim 1 , wherein the carbon included in the negative electrode material (SiOx-C) has an R value, defined as a ratio Id/Ig of a peak Id in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1300 cm −1 and 1400 cm −1 to a peak Ig in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1530 cm −1 and 1630 cm −1 , is 0.5 or more.
6. The lithium ion secondary battery according to claim 4 , wherein the carbon included in the negative electrode material (SiOx-C) has an R value, defined as a ratio Id/Ig of a peak Id in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1300 cm −1 and 1400 cm −1 to a peak Ig in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1530 cm −1 and 1630 cm −1 , is more than 0.5.
7. The lithium ion secondary battery according to claim 4 , wherein the carbon included in the negative electrode material (SiOx-C) has an R value, defined as a ratio Id/Ig of a peak Id in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1300 cm −1 and 1400 cm −1 to a peak Ig in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1530 cm −1 and 1630 cm −1 , is from 0.7 to 1.3.
8. The lithium ion secondary battery according to claim 4 , wherein the carbon included in the negative electrode material (SiOx-C) has an R value, defined as a ratio Id/Ig of a peak Id in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1300 cm −1 and 1400 cm −1 to a peak Ig in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1530 cm −1 and 1630 cm −1 , is from 0.8 to 1.2.
9. The lithium ion secondary battery according to claim 1 , wherein the content of the carbon included in the negative electrode material (SiOx-C) with respect to the whole negative electrode material (SiOx-C) is from 0.5 mass % to 4.0 mass % and wherein the carbon included in the negative electrode material (SiOx-C) has an R value, defined as a ratio Id/Ig of a peak Id in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1300 cm −1 and 1400 cm −1 to a peak Ig in a profile obtained by laser Raman spectrometry with an excitation wavelength of 532 nm observed between 1530 cm −1 and 1630 cm −1 , is more than 0.5 and 1.5 or less.
10. The lithium ion secondary battery according to claim 1 , wherein the carbon over a part or a whole of the surface of the oxide of silicon is obtained by heat-treating a mixture of particles of an oxide of silicon and coal pitch.
11. The lithium ion secondary battery according to claim 1 , wherein the crystallite size of the silicon crystallites is from 3 nm to 6 nm.
12. The lithium ion secondary battery according to claim 1 , wherein the ratio of the negative electrode material (SiOx-C) to the carbonaceous negative electrode material (C) is from 1:99 to 10:90 in terms of mass.
13. The lithium ion secondary battery according to claim 5 , wherein the R value is from 0.7 to 1.3.
14. The lithium ion secondary battery according to claim 5 , wherein the R value is from 0.8 to 1.2.
15. The lithium ion secondary battery according to claim 9 , wherein the ratio of the negative electrode material (SiOx-C) to the carbonaceous negative electrode material (C) is from 1:99 to 10:90 in terms of mass.
16. The lithium ion secondary battery according to claim 11 , wherein the ratio of the negative electrode material (SiOx-C) to the carbonaceous negative electrode material (C) is from 1:99 to 10:90 in terms of mass.
17. The lithium ion secondary battery according to claim 10 , wherein the ratio of the negative electrode material (SiOx-C) to the carbonaceous negative electrode material (C) is from 1:99 to 10:90 in terms of mass.