Sulfide solid electrolyte

1. A sulfide solid electrolyte, comprising:

Lithium;

Phosphorus;

Sulfur; and

chlorine,

wherein a molar ratio of the chlorine to the phosphorus, c (Cl/P), is greater than 1.0 and 1.9 or less, and the sulfide solid electrolyte has an argyrodite-type crystal structure having a lattice constant in a range of 9.750 Å to 9.820 Å.

2. The sulfide solid electrolyte according to claim 1 , wherein a lattice constant of the argyrodite-type crystal structure is 9.795 Å or more and 9.820 Å or less.

3. The sulfide solid electrolyte according to claim 1 , wherein a lattice constant of the argyrodite-type crystal structure is 9.795 Å or more and 9.815 Å or less.

4. The sulfide solid electrolyte according to claim 1 , wherein the argyrodite-type crystal structure has diffraction peaks at 2θ=25.5±0.5 deg and 30.0±0.5 deg in powder X-ray diffraction using CuKα rays.

5. The sulfide solid electrolyte according to claim 1 , wherein a molar ratio of the lithium to the phosphorus, a (Li/P), a molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the chlorine to the

phosphorus, c (C/P), satisfy formulas (A) to (C): 5.0≤a≤6.5 (A); 6.1≤a+c≤7.5 (B); and 0.5≤a−b≤1.5 (C), and b>0 and c>1.0 are satisfied.

6. The sulfide solid electrolyte according to claim 1 , having a composition of formula (1): Li a PS b Cl c , (1),

wherein a to c satisfy formulas (A) to (C): 5.0≤a≤6.5 (A); 6.1≤a+c≤7.5 (B); and 0.5≤a−b≤1.5 (C), and b>0 and c>1.0 are satisfied.

7. The sulfide solid electrolyte according to claim 1 , wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak at 2θ=50.3+0.5 deg, or, if the sulfide solid electrolyte has a diffraction peak, said diffraction peak satisfies formula (2), 0<I A /I B <0.05 (2), where I A represents intensity of a diffraction peak at 2θ=50.3±0.5 deg, and I B represents intensity of a diffraction peak at 2θ=25.5±0.5 deg.

8. The sulfide solid electrolyte according to claim 1 , wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak (not a peak arising from an argyrodite-type crystal structure) at 2θ=17.6±0.4 deg and 2θ=18.1±0.4 deg, or, if the sulfide solid electrolyte has a diffraction peak, said diffraction peak satisfies formula (3), 0<I c /I D <0.05 (3), where I C represents intensity of a diffraction peak which is not a diffraction peak arising from the argyrodite-type crystal structure between the diffraction peaks at 2θ=17.6±0.4 deg and 2θ=18.1±0.4 deg, and I D represents intensity of a diffraction peak at 2θ=30.0±0.5 deg.

9. The sulfide solid electrolyte according to claim 1 , wherein, in a solid 31 P-NMR measurement, the sulfide solid electrolyte has a peak in each of regions 80.3 to 81.7 ppm, 82.4 to 83.7 ppm and 84.0 to 85.6 ppm; and an area ratio of the peak in the region of 80.3 to 81.7 ppm to a total area of all peaks in the region of 78 to 92 ppm is 40% or more.

10. An electrode mix, comprising the sulfide solid electrolyte according to claim 1 and an active material.

11. A lithium ion battery, comprising the electrode mix according to claim 10 .

12. An electrode mix, produced from the sulfide solid electrolyte according to claim 1 .

13. A lithium ion battery, comprising the electrode mix according to claim 12 .

14. The sulfide solid electrolyte according to claim 4 , wherein a molar ratio of the lithium to the phosphorus, a (Li/P), a molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the chlorine to the phosphorus, c (Cl/P), satisfy formulas (A) to (C): 5.0≤a≤6.5 (A); 6.1≤a+c≤7.5 (B); and 0.5≤a−b≤1.5 (C), and b>0 and c>1.0 are satisfied.

15. The sulfide solid electrolyte according to claim 4 , having a composition represented by formula (1), Li a PS b Cl c (1),

wherein a to c satisfy formulas (A) to (C): 5.0≤a≤6.5 (A); 6.1≤a+c≤7.5 (B); and 0.5≤a−b≤1.5 (C), and b>0 and c>1.0 are satisfied.

16. The sulfide solid electrolyte according to claim 4 , wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak at 2θ=50.3±0.5 deg, or, if the sulfide solid electrolyte has a diffraction peak, said diffraction peak satisfies formula (2), 0<I A /I B <0.05 (2), where I A represents intensity of a diffraction peak at 2θ=50.3±0.5 deg, and I B represents intensity of a diffraction peak at 2θ=25.5±0.5 deg.

17. The sulfide solid electrolyte according to claim 4 , wherein, in a solid 31 P-NMR measurement, the sulfide solid electrolyte has a peak in each of regions 80.3 to 81.7 ppm, 82.4 to 83.7 ppm and 84.0 to 85.6 ppm; and an area ratio of the peak in the region of 80.3 to 81.7 ppm to a total area of all peaks in the region of 78 to 92 ppm is 40% or more.

18. The sulfide solid electrolyte according to claim 5 , wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak at 2θ=50.3±0.5 deg, or, if the sulfide solid electrolyte has a diffraction peak, said diffraction peak satisfies formula (2), 0<I B <0.05 (2), where I A represents intensity of a diffraction peak at 2θ=50.3±0.5 deg, and I n represents intensity of a diffraction peak at 2θ=25.5±0.5 deg.

19. The sulfide solid electrolyte according to claim 5 , wherein, in a solid 31 P-NMR measurement, the sulfide solid electrolyte has a peak in each of regions 80.3 to 81.7 ppm, 82.4 to 83.7 ppm and 84.0 to 85.6 ppm; and an area ratio of the peak in the region of 80.3 to 81.7 ppm to a total area of all peaks in the region of 78 to 92 ppm is 40% or more.

20. The sulfide solid electrolyte according to claim 6 , wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak at 2θ=50.3±0.5 deg, or, if the sulfide solid electrolyte has a diffraction peak, said diffraction peak satisfies formula (2), 0<I A /I B <0.05 (2), where I A represents intensity of a diffraction peak at 2θ=50.3±0.5 deg, and I B represents intensity of a diffraction peak at 2θ=25.5±0.5 deg.

21. The sulfide solid electrolyte according to claim 6 , wherein, in a solid 31 P-NMR measurement, the sulfide solid electrolyte has a peak in each of regions 80.3 to 81.7 ppm, 82.4 to 83.7 ppm and 84.0 to 85.6 ppm; and an area ratio of the peak in the region of 80.3 to 81.7 ppm to a total area of all peaks in the region of 78 to 92 ppm is 40% or more.

22. The sulfide solid electrolyte according to claim 7 , wherein, in a solid 31 P-NMR measurement, the sulfide solid electrolyte has a peak in each of regions 80.3 to 81.7 ppm, 82.4 to 83.7 ppm and 84.0 to 85.6 ppm; and an area ratio of the peak in the region of 80.3 to 81.7 ppm to a total area of all peaks in the region of 78 to 92 ppm is 40% or more.