A sulfide solid electrolyte may include lithium, phosphorus and sulfur, and the sulfide solid electrolyte may have a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 29.7±0.5 deg in powder X-ray diffraction using CuKα rays, and a crystallite diameter in a range of from 5 to 20 nm.

The present invention concerns a method for producing a solid material according to general formula (I) as follows: Li.sub.6-.sub.x_.sub.2yCu.sub.xPS.sub.5_.sub.yX (I) wherein X is selected from the group consisting of: F, CI, I and Br; 0.005 ≤ x ≤ 5; and 0 ≤y ≤ 0.5.; comprising at least bringing at least lithium sulfide, phosphorous sulfide, halogen compound and a copper compound, optionally in one or more solvents. The invention also refers to said solid materials and their use as solid electrolytes notably for electrochemical devices.

A process for producing a low-cost water-reactive sulfide material includes reacting a substantially anhydrous first alkali metal salt, a substantially anhydrous first sulfide compound, and a substantially anhydrous first alkali metal hydrosulfide compound in a substantially anhydrous polar solvent, providing differential solubility for a substantially high solubility second sulfide and a substantially low solubility second alkali metal salt, and forming a mixture of the high solubility second sulfide, a second alkali metal hydrosulfide, and the low solubility second alkali metal salt; removing the low solubility second alkali metal salt to isolate the supernatant including the second sulfide, and separating the polar solvent from the second sulfide and the second alkali metal hydrosulfide followed by heating to produce the second sulfide. The present disclosure provides a scalable process for production of a high purity alkali metal sulfide that is essentially free of undesired contaminants.

A method for producing a sulfide solid electrolyte includes a firing step of firing a raw material containing Li.sub.2S in a hydrogen sulfide-containing atmosphere at a temperature of 300° C. or higher, Li.sub.2S having a purity of 50 to 90% by mass at the start of firing. The Li.sub.2S may contain impurities including at least one of LiOH, Li.sub.2O, LiHCO.sub.3, and Li.sub.2CO.sub.3. In the firing step, it is preferable that a concentration of a hydrogen sulfide in the hydrogen sulfide-containing atmosphere is 50 volume % or more. It is preferable that the raw material further contains P.sub.2S.sub.5 and LiX (X represents at least one type of elemental halogen), and the sulfide solid electrolyte has an argyrodite-type crystal structure.

An apparatus for producing lithium sulfide, including: a reaction container for allowing lithium hydroxide powder to be in contact with a hydrogen sulfide gas; a stirring blade inside the reaction container; a first heating apparatus that keeps the temperature of an inner wall of the reaction container that is in contact with the powder; and a second heating apparatus that keeps the temperature of an inner wall that is not in contact with the powder.

An apparatus for producing lithium sulfide, including: a reaction container for allowing lithium hydroxide powder to be in contact with a hydrogen sulfide gas; a stirring blade inside the reaction container; a first heating apparatus that keeps the temperature of an inner wall of the reaction container that is in contact with the powder; and a second heating apparatus that keeps the temperature of an inner wall that is not in contact with the powder.

Provided is a method of producing a solid electrolyte having high ionic conductivity using a liquid phase method, including a first step of mixing two or more compounds satisfying (1) and a complexing agent 1 satisfying (2), and a second step of further mixing in a complexing agent 2 satisfying (3) after the first step. (1) A compound containing one or more selected from a group consisting of a lithium element, a sulfur element, a phosphorus element and a halogen element. (2) A complexing agent capable of forming a complex containing Li.sub.3PS.sub.4 and a halogen element. (3) A complexing agent other than the complexing agent 1, capable of forming a complex containing Li.sub.3PS.sub.4.

Provided is a sulfide-based inorganic solid electrolyte material having lithium ionic conductivity, in which the sulfide-based inorganic solid electrolyte material has a particle shape, and when a mode diameter in a number average particle size distribution of the sulfide-based inorganic solid electrolyte material that is obtained from an observed image of a scanning electron microscope (SEM) is represented by Dm [μm] and a particle size corresponding to a cumulative frequency of 90% in the number average particle size distribution is represented by D.sub.90 [μm], a value of D.sub.90/Dm is 1.6 or more and 8.0 or less.

A compound of Formula 1:
Li.sub.1+2x−yZn.sub.1−xPS.sub.4−y−δA.sub.y  (1)
wherein A is halogen, 0≤x≤1, 0≤y≤0.5, and 0≤δ≤0.5, and wherein the compound of Formula 1 has an body centered cubic crystal structure. Also a lithium battery and an electrode including the compound.

A positive electrode for an all-solid secondary battery, comprising a positive electrode active material expressed by A.sub.2S.AX, wherein

A is an alkali metal; and

X is selected from I, Br, Cl, F, BF.sub.4, BH.sub.4, SO.sub.4, BO.sub.3, PO.sub.4, O, Se, N, P, As, Sb, PF.sub.6, AsF.sub.6, ClO.sub.4, NO.sub.3, CO.sub.3, CF.sub.3SO.sub.3, CF.sub.3COO, N(SO.sub.2F).sub.2 and N(CF.sub.3SO.sub.2).sub.2.