Solid electrolyte

1. A method of producing a crystallized solid electrolyte wherein the solid electrolyte has a peak in a peak region of 75.0 ppm or more and 80.0 ppm or less in a 31 P-NMR spectrum, the method comprising:

producing a solid electrolyte from a raw material and a compound comprising a halogen element; and

heating the solid electrolyte to obtain the crystallized solid electrolyte;

wherein the raw material comprises: (i) lithium sulfide and phosphorus sulfide, (ii) sulfur and phosphorus, (iii) phosphorus sulfide and sulfur, or (iv) phosphorus sulfide, sulfur, and phosphorus.

2. The method according to claim 1 , wherein the compound comprising a halogen element is a compound represented by formula (E′):

M w X x   (E′)

where:

M is Li, B, Al, Si, P, S, Ge, As, Se, Sn, Sb, Te, Pb, or Bi;

X is F, Cl, Br, or I;

w is an integer of 1 or 2; and

x is an integer of from 1 to 10.

3. The method according to claim 1 , wherein M is P, and X is Br, I, or Cl.

4. The method according to claim 1 , wherein M is Li, and X is Br, I, or Cl.

5. The method according to claim 1 , wherein M is Li, and X is Br or Cl.

6. The method according to claim 1 , wherein the solid electrolyte is amorphous and has two crystallization peaks in a thermo gravimetric-differential thermal measurement.

7. The method according to claim 6 , wherein heating the solid electrolyte comprises heating at a temperature between the temperatures indicated by the two crystallization peaks.

8. The method according to claim 6 , wherein the two crystallization peaks appear in a range of 150° C. or higher and 360° C. or lower.

9. The method according to claim 6 , wherein a distance between the two crystallization peaks is 20 to 100° C.

10. The method according to claim 1 , wherein heating the solid electrolyte comprises heating at a dew point of −40° C. or less.

11. The method according to claim 1 , wherein heating the solid electrolyte comprises heating for a period of 0.005 minutes to 10 hours.

12. The method according to claim 1 , wherein:

the raw material comprises lithium sulfide and phosphorus pentasulfide; and

a molar ratio of lithium sulfide to phosphorus pentasulfide is 60:40 to 90:10.

13. The method according to claim 12 , wherein a molar ratio of total moles of lithium sulfide and phosphorus pentasulfide to total moles of the compound comprising a halogen element is 50:50 to 99:1.

14. The method according to claim 12 , wherein producing the solid electrolyte comprises treating lithium sulfide, phosphorus pentasulfide, and the compound comprising a halogen element by a melt extraction method, a mechanical milling method, a slurry method, a solid-phase method, or by a combination of two or more such methods.

15. The method according to claim 12 , wherein producing the solid electrolyte comprises:

(a) milling after mixing lithium sulfide, phosphorus pentasulfide, and the compound comprising a halogen element;

(b) milling lithium sulfide and phosphorus pentasulfide, followed by further milling after adding the compound comprising a halogen element;

(c) milling the compound comprising a halogen element and phosphorus pentasulfide, followed by further milling after adding lithium sulfide;

(d) milling lithium sulfide and the compound comprising a halogen element, followed by further milling after adding phosphorus pentasulfide; or

(e) mixing a first mixture obtained by mixing and milling lithium sulfide and the compound comprising a halogen element and a second mixture obtained by mixing and milling the compound comprising a halogen element and phosphorus pentasulfide, followed by further milling.

16. The method according to claim 12 , wherein producing the solid electrolyte comprises:

subjecting lithium sulfide and phosphorus pentasulfide to mechanical milling, mixing the compound comprising a halogen element, and treating the resulting mixture by the solid phase method; or

mixing a first product obtained by treating lithium sulfide and phosphorus pentasulfide by the solid phase method and a second product obtained by treating phosphorus pentasulfide and the compound comprising a halogen element by the melt extraction method are mixed, and treating the resulting mixture by the slurry method.

17. The method according to claim 12 , wherein a total content of a lithium salt of a sulfur oxide of lithium sulfide is 0.15 mass % or less.