Sulfide solid electrolyte

1. A sulfide solid electrolyte, comprising lithium, phosphorus, sulfur, and two or more of elements X selected from the group consisting of halogen elements,

wherein the sulfide solid electrolyte comprises an argyrodite-type crystal structure, and

wherein a molar ratio of the sulfur to the phosphorus, b (S/P), and a molar ratio of the elements X to the phosphorus, c (X/P), satisfy formula (1):

0.23< c/b< 0.57  (1).

2. The sulfide solid electrolyte according to claim 1 , wherein the molar ratio of the sulfur to the phosphorus, b (S/P),and the molar ratio of the elements X to the phosphorus, c (X/P), satisfy formula (1a):

0.25≤ c/b≤ 0.43  (1a).

3. The sulfide solid electrolyte according to claim 1 , wherein the molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the elements X to the phosphorus, c (X/P), satisfy formula (1b):

0.30≤ c/b≤ 0.41  (1b).

4. The sulfide solid electrolyte according to claim 1 , wherein at least one of the elements X is chlorine.

5. The sulfide solid electrolyte according to claim 4 , satisfying formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X.

6. The sulfide solid electrolyte according to claim 4 ,

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X; and

wherein at least one of the elements X is bromine.

7. The sulfide solid electrolyte according to claim 4 ,

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X;

wherein at least one of the elements X is bromine; and

wherein a molar ratio of the lithium to the phosphorus, a (Li/P), the molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the elements X to the phosphorus, c (X/P), satisfy formulas (A) to (C):

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

8. The sulfide solid electrolyte according to claim 4 ,

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X;

wherein at least one of the elements X is bromine; and

wherein the sulfide solid electrolyte comprises a composition represented by formula (3):

Li a (P 1-α M α )S b X c   (3)

wherein:

M is one or more of elements selected from the group consisting of Si, Ge,Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is two or more of elements selected from the group consisting of F, Cl, Br and I;

a to c satisfy formulas (A) to (C); and

α satisfies 0≤α≤0.3:

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

9. The sulfide solid electrolyte according to claim 4 ,

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X;

wherein diffraction peaks are measured at 2θ=25.2±0.5 deg and 29.7±0.5 deg in powder X-ray diffraction using CuKα rays; and

wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak derived from lithium halide, or if the sulfide solid electrolyte has a diffraction peak derived from lithium halide, said diffraction peak satisfies formula (4):

0< I A /I B <0.1  (4)

wherein I A represents an intensity of a diffraction peak of lithium halide, and I B represents an intensity of a diffraction peak at 2θ=25.2±0.5 deg.

10. The sulfide solid electrolyte according to claim 4 ,

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X;

wherein diffraction peaks are measured at 2θ=25.2±0.5 deg and 29.7±0.5 deg in powder X-ray diffraction using CuKα rays; and

wherein, in powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte does not have a diffraction peak at 2θ=17.6±0.4 deg and 2θ=18.1±0.4 deg, or if the sulfide solid electrolyte has a diffraction peak at 2θ=17.6±0.4 deg and 2θ=18.1±0.4 deg, said diffraction peak satisfies formula (5):

0< I C /I D <0.05  (5)

wherein I C represents an intensity of a diffraction peak which is not a diffraction peak of an 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 an intensity of a diffraction peak at 2θ=29.7±0.5 deg.

11. The sulfide solid electrolyte according to claim 1 , wherein diffraction peaks are measured at 2θ=25.2±0.5 deg and 29.7±0.5 deg in powder X-ray diffraction using CuKα rays.

12. The sulfide solid electrolyte according to claim 1 , wherein at least one of the elements X is bromine.

13. The sulfide solid electrolyte according to claim 1 , wherein a molar ratio of the lithium to the phosphorus, a (Li/P), the molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the elements X to the phosphorus, c (X/P), satisfy formulas (A) to (C):

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

14. The sulfide solid electrolyte according to claim 1 , comprising a composition represented by formula (3):

Li a (P 1-α M α )S b X c   (3)

wherein:

M is one or more of elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is two or more of elements selected from the group consisting of F, Cl, Br and I;

a to c satisfy formulas (A) to (C); and

a satisfies 0≤α≤0.3:

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

15. The sulfide solid electrolyte according to claim 1 , wherein:

at least one of the elements X is chlorine; and

at least one of the elements X is bromine.

16. The sulfide solid electrolyte according to claim 1 ,

wherein at least one of the elements X is chlorine;

wherein at least one of the elements X is bromine; and

wherein a molar ratio of the lithium to the phosphorus, a (Li/P), the molar ratio of the sulfur to the phosphorus, b (S/P), and the molar ratio of the elements X to the phosphorus, c (X/P), satisfy formulas (A) to (C):

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

17. The sulfide solid electrolyte according to claim 1 ,

wherein at least one of the elements X is bromine;

wherein the sulfide solid electrolyte satisfies formula (2):

0.25<X Cl <1  (2)

wherein X Cl represents a molar ratio of the chlorine to the elements X; and

wherein the sulfide solid electrolyte comprises a composition represented by formula (3):

Li a (P 1-α M α )S b X c   (3)

wherein:

M is one or more of elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is two or more of elements selected from the group consisting of F, Cl, Br and I;

a to c satisfy formulas (A) to (C); and

a satisfies 0≤α≤0.3:

5.0≤ a≤ 7.5  (A)

6.5≤ a+c≤ 7.5  (B)

0.5≤ a−b≤ 1.5  (C)

wherein b>0 and c>0 are satisfied.

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

19. A lithium ion battery, comprising the electrode mix according to claim 18 .

20. A lithium ion battery, comprising the sulfide solid electrolyte according to claim 1 .