The solid electrolyte material of the present disclosure includes Li, Ca, Y, Sm, X, and O, wherein X is at least one selected from the group consisting of F, Cl, Br, and I.

A production method for producing a halide, the method includes a heat treatment step of heat-treating a mixed material containing (NH.sub.4).sub.aYα.sub.3+a, (NH.sub.4).sub.bSmβ.sub.3+b, Liγ, and Caδ.sub.2 in an inert gas atmosphere, wherein α, β, γ, and δ are each independently at least one selected from the group consisting of F, Cl, Br, and I, and the following three formulas: 0≤a≤3, 0≤b≤3, and 0<a+b≤6, are satisfied.

The production method of the present disclosure includes heat-treating a material mixture containing a compound containing Y, a compound containing Sm, NH.sub.4α, Liβ, and Caγ.sub.2 in an inert gas atmosphere. The compound containing Y is at least one selected from the group consisting of Y.sub.2O.sub.3 and Yδ.sub.3, and the compound containing Sm is at least one selected from the group consisting of Sm.sub.2O.sub.3 and Smε.sub.3. The material mixture contains at least one selected from the group consisting of Y.sub.2O.sub.3 and Sm.sub.2O.sub.3, and α, β, γ, δ, and ε are each independently at least one selected from the group consisting of F, Cl, Br, and I.

The production method of the present disclosure includes heat-treating a material mixture containing a compound containing Y, a compound containing Sm, NH.sub.4α, Liβ, and Caγ.sub.2 in an inert gas atmosphere. The compound containing Y is at least one selected from the group consisting of Y.sub.2O.sub.3 and Yδ.sub.3, and the compound containing Sm is at least one selected from the group consisting of Sm.sub.2O.sub.3 and Smε.sub.3. The material mixture contains at least one selected from the group consisting of Y.sub.2O.sub.3 and Sm.sub.2O.sub.3, and α, β, γ, δ, and ε are each independently at least one selected from the group consisting of F, Cl, Br, and I.

A sulfide solid electrolyte, which is able to adjust the morphology unavailable traditionally, or is readily adjusted so as to have a desired morphology, the sulfide solid electrolyte having a volume-based average particle diameter measured by laser diffraction particle size distribution measurement of 3 μm or more and a specific surface area measured by the BET method of 20 m.sup.2/g or more; and a method of treating a sulfide solid electrolyte including the sulfide solid electrolyte being subjected to at least one mechanical treatment selected from disintegration and granulation.

Provided is a sulfide-based solid electrolyte which is capable of suppressing the generation of hydrogen sulfide caused by reaction with moisture even when in contact with dry air in a dry room or the like, and capable of maintaining lithium ion conductivity. Proposed is a sulfide-based solid electrolyte for a lithium secondary battery, wherein the surface of a compound containing lithium, phosphorus, sulfur, and halogen, and having a cubic argyrodite-type crystal structure is coated with a compound containing lithium, phosphorus, and sulfur, and having a non-argyrodite-type crystal structure.

Provided is a sulfide-based solid electrolyte which is capable of suppressing the generation of hydrogen sulfide caused by reaction with moisture even when in contact with dry air in a dry room or the like, and capable of maintaining lithium ion conductivity. Proposed is a sulfide-based solid electrolyte for a lithium secondary battery, wherein the surface of a compound containing lithium, phosphorus, sulfur, and halogen, and having a cubic argyrodite-type crystal structure is coated with a compound containing lithium, phosphorus, and sulfur, and having a non-argyrodite-type crystal structure.

A solid electrolyte, in which a part of an element contained in a mobile ion-containing material is substituted, and an occupied impurity level that is occupied by electrons or an unoccupied impurity level that is not occupied by electrons is provided between a valence electron band and a conduction band of the mobile ion-containing material, and a smaller energy difference out of an energy difference between a highest level of energy in the occupied impurity level and an energy and a LUMO level difference between a lowest level of energy in the unoccupied impurity level and a HOMO level is greater than 0.3 eV.

A conductive film that includes particles of a layered material including one or plural layers, wherein the one or plural layers include a layer body represented by: M.sub.mX.sub.n, wherein M is at least one metal of Group 3, 4, 5, 6, or 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 to 4, and m is more than n and 5 or less, and a modifier or terminal T exists on a surface of the layer body, wherein T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, or a hydrogen atom, and wherein a χ-axis direction rocking curve half-value width for a peak of a (001) plane (1 is a natural number multiple of 2) obtained by X-ray diffraction measurement of the conductive film is 10.3° or less.

A solid electrolyte composition includes: an inorganic solid electrolyte (A) having ion conductivity of a metal belonging to Group 1 or Group 2 in the periodic table; a binder (B); and a dispersion medium (C), in which the binder (B) includes a first binder (B1) that precipitates by a centrifugal separation process and a second binder (B2) that does not precipitate by the centrifugal separation process, the centrifugal separation process being performed in the dispersion medium (C) under a specific condition, and a content X of the first binder (B1) and a content Y of the second binder (B2) satisfy the following expression,
0.10≤Y/(X+Y)≤0.80.