A sulfide solid electrolyte to be used in a lithium-ion secondary battery, including an argyrodite crystal, in which the crystal is represented by a composition formula Li.sub.a—M—Z.sub.b—Ha.sub.c; M is at least one element selected from Na, K, and elements each of which exists as any of divalent to pentavalent cations in the crystal; Z is at least one element selected from elements that exists as a divalent anion in the crystal; Z includes S; Ha is at least one element selected from the group consisting of F, Cl, Br, and I; a, b, and c in the composition formula indicate a ratio among contents (unit: at%) of the respective elements and satisfy 5 < a < 7, 4 < b < 6, and 0 < c < 2; and a maximum distance between Li ions in the crystal is 2.54 Å or shorter.

Provided are sulfide-based solid electrolyte with good ionic conductivity and an all-solid lithium ion battery using the same. A sulfide-based solid electrolyte having an argyrodite-type structure, wherein a composition of the sulfide-based solid electrolyte is represented by the formula:

Li.sub.8GeS.sub.5-xTe.sub.1+x

in which: −0.5≤x<0, 0<x≤0.375.

A process for preparing a solid electrolyte that includes mixing a lithium source with a sulfur source and a compound containing phosphorous and sulfur to form a composite, then heating the composite to the melting point of the compound containing phosphorous and sulfur to form the solid electrolyte material. A solid electrolyte material prepared by the process, wherein the solid electrolyte material is of formula I, which is Li.sub.(7−y−z)PS.sub.(6−y−z)X.sub.(y)W.sub.(z) wherein X and W are individually selected from F, Cl, Br, and I; where y and z each individually range from 0 to 2; and where y+z ranges from 0 to 2.

Provided are a solid electrolyte composition including an inorganic solid electrolyte, binder particles, and a dispersion medium, in which the inorganic solid electrolyte has a conductivity of ions of metals belonging to Group I or II of the periodic table and includes a sulfur atom, and the binder particles are constituted of a polymer having a macromonomer having a mass average molecular weight of 1,000 or more combined therewith as a side chain component and having at least one group from a group of functional groups (b) below, an electrode sheet for a battery and an all solid state secondary battery which are produced using the solid electrolyte composition, a method for manufacturing an electrode sheet for a battery, and a method for manufacturing an all solid state secondary battery. group of functional groups (b) a carboxyl group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group.

Methods for the scalable and systematic synthesis of semiconducting Chevrel phase compounds via self-propagating high temperature synthesis (SHS) are provided. The provided methods utilize elemental precursors not utilized by typical synthesis methods. The precursors may include molybdenum (Mo), molybdenum disulfide (MoS.sub.2), and a ternary cation. In various aspects, the ternary cation may be copper (Cu), iron (Fe), or nickel (Ni). The utilization of the provided precursors and SHS decreases the time it takes to synthesize Chevrel phase compounds as compared to typical heat treatment methods.

According to one embodiment of the present invention, provided is an ionic conductor comprising lithium (Li), borohydride (BH.sub.4.sup.−), phosphorus (P), and sulfur (S), wherein, in X-ray diffraction (CuKα: λ=1.5405 Å), the ionic conductor has diffraction peaks, at least, at 2θ=14.4±1.0 deg, 15.0±1.0 deg, 24.9±1.0 deg, 29.2±1.5 deg, 30.3±1.5 deg, 51.1±2.5 deg and 53.5±2.5 deg.

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 sulfide solid electrolyte containing lithium, phosphorus, sulfur; and one or more of elements X selected from the group consisting of halogen elements and chalcogen elements excluding sulfur, wherein the sulfide solid electrolyte includes an argyrodite-type crystal structure, and 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 a molar ratio of the element X to the phosphorus, c (X/P), satisfy formulas (1) to (3): 5.0≤a≤7.1 (1) 1.0<a−b≤1.5 (2) 6.5≤a+c<7.1 (3) wherein b>0 and c>0 are satisfied.

A sulfide solid electrolyte containing lithium, phosphorus, sulfur; and one or more of elements X selected from the group consisting of halogen elements and chalcogen elements excluding sulfur, wherein the sulfide solid electrolyte includes an argyrodite-type crystal structure, and 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 a molar ratio of the element X to the phosphorus, c (X/P), satisfy formulas (1) to (3): 5.0≤a≤7.1 (1) 1.0<a−b≤1.5 (2) 6.5≤a+c<7.1 (3) wherein b>0 and c>0 are satisfied.

A method for preparing a lithium ion conductive sulfide, which is capable of independently controlling the elemental ratio of lithium (Li), phosphorus (P), sulfur (S), etc, is provided. The method for preparing a lithium ion conductive sulfide can provide a lithium ion conductive sulfide having a crystal structure and an anion cluster distribution distinguished from those of existing ones.