Negative electrode active material, raw material for a negative electrode active material, negative electrode, lithium ion secondary battery, method for producing a negative electrode active material, and method for producing a lithium ion secondary battery

1. A negative electrode active material comprising:

a particle of negative electrode active material containing silicon-based material consisting of SiO x (0.5≤x≤1.6);

wherein the intensity A of a peak in a Si-region given in the chemical shift region of from −50 to −95 ppm and the intensity B of a peak in a SiO 2 -region given in the chemical shift region of from −96 to −150 ppm in a 29 Si-MAS-NMR spectrum of the silicon-based material satisfy a relationship that A/B≥2.

2. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has a peak given in the chemical shift region of from −70 to −85 ppm in a 29 Si-MAS-NMR spectrum.

3. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has at least two peaks given in the chemical shift region of from −50 to −95 ppm in a 29 Si-MAS-NMR spectrum.

4. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has at least one peak corresponding to any one or more of Li 2 SiO 3 and Li 4 SiO 4 in a region given in the chemical shift region of from −50 to −95 ppm in a 29 Si-MAS-NMR spectrum.

5. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has a peak corresponding to metal Si in a region given in the chemical shift region of from −50 to −95 ppm in a 29 Si-MAS-NMR spectrum.

6. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material contains any one or more of Li 2 SiO 3 , Li 4 SiO 4 , Li 2 O, and Li 2 CO 3 .

7. The negative electrode active material according to claim 6 , wherein the particle of negative electrode active material contains any two or more of Li 2 SiO 3 , Li 4 SiO 4 , Li 2 O, and Li 2 CO 3 .

8. The negative electrode active material according to claim 6 , wherein the Li 2 SiO 3 has a diffraction peak near 38.2680° in which the full width at half maximum (2θ) is 0.75° or more in an X-ray diffraction.

9. The negative electrode active material according to claim 6 , wherein the Li 4 SiO 4 has a diffraction peak near 23.9661° in which the full width at half maximum (2θ) is 0.2° or more in an X-ray diffraction.

10. The negative electrode active material according to claim 6 , wherein the Li 2 SiO 3 and the Li 4 SiO 4 are amorphous.

11. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material contains a fluorine compound in the form of an island, a film, or an unevenness on at least a part of its surface.

12. The negative electrode active material according to claim 11 , wherein the fluorine compound is lithium fluoride or a decomposition product of LiPF 6 .

13. The negative electrode active material according to claim 1 , wherein the negative electrode active material has a diffraction peak attributable to (111) crystal face in which the full width at half maximum (2θ) is 1.2° or more in an X-ray diffraction, and the size of the crystallite corresponding to the crystal face is 7.5 nm or less.

14. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has a median diameter of 0.5 μm or more and 20 μm or less.

15. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has carbon material on its surface.

16. The negative electrode active material according to claim 15 , wherein the average thickness of the coating carbon material is 1 nm or more and 5000 nm or less.

17. The negative electrode active material according to claim 1 , wherein the particle of negative electrode active material has SiO x , carbon, and a fluorine compound or has SiO, and a fluorine compound at least partially.

18. The negative electrode active material according to claim 11 , wherein the mean coverage of the coating layer consisting of the fluorine compound is 30% or more.

19. The negative electrode active material according to claim 15 , wherein the mean coverage of the coating layer consisting of the carbon material is 30% or more.

20. A raw material for a negative electrode active material comprising the negative electrode active material according to claim 1 ; and a carbon material.

21. A negative electrode comprising:

a negative electrode active material layer formed by the raw material for a negative electrode active material according to claim 20 ; and

a negative electrode current collector, wherein

the negative electrode active material layer is formed on the negative electrode current collector; and

the negative electrode current collector contains carbon and sulfur, and each content is 100 ppm or less.

22. A lithium ion secondary battery, wherein the lithium ion secondary battery uses a negative electrode containing the negative electrode active material according to claim 1 .

23. A method for producing a negative electrode active material containing a particle of negative electrode active material which contains silicon-based material consisting of SiO x , comprising:

selecting and then using a silicon-based material wherein the x is 0.5 or more and 1.6 or less and the intensity A of a peak in a Si-region given in the chemical shift region of from −50 to −95 ppm and the intensity B of a peak in a SiO 2 -region given in the chemical shift region of from −96 to −150 ppm in a 29 Si-MAS-NMR spectrum satisfy a relationship that A/B≥2.

24. A method for producing a lithium ion secondary battery, comprising:

preparing a negative electrode by using a negative electrode active material made by the method for producing a negative electrode active material according to claim 23 ; and

producing a lithium ion secondary battery by using the prepared negative electrode.