A doped phosphorus-sulfur iodide solid electrolyte, a preparation method therefor, and use thereof. The chemical formula of said solid electrolyte is Li.sub.6-xM.sub.xP.sub.1-xS.sub.5I, in which 0<x<0.8, and M is tungsten and/or molybdenum. Said method comprises: 1) mixing a lithium source, a phosphorus source, an iodine source, a sulfur source, and an M source in an inert atmosphere, and then ball-milling same to obtain a solid electrolyte precursor; and 2) sintering the solid electrolyte precursor obtained in step 1) in an inert atmosphere or in vacuum to obtain the doped phosphorus-sulfur iodide solid electrolyte.

A composite containing phosphorus, lithium, iron, sulfur, and carbon as constituent elements wherein lithium sulfide (Li.sub.2S) is present in an amount of 90 mol % or more, and wherein the crystallite size calculated from the half-width of a diffraction peak based on the (111) plane of Li.sub.2S as determined by X-ray powder diffraction measurement is 80 nm or less. The composite exhibits a high capacity (in particular, a high discharge capacity) useful as an electrode active material for a lithium-ion secondary battery (in particular, a cathode active material for a lithium-ion secondary battery), without the need for stepwise pre-cycling treatment.

The present invention concerns a new solid material according to general formula (I) as follows: Li.sub.4−2xZn.sub.xP.sub.2S.sub.6 (I) wherein 0<x≤1. The invention also refers to a method for producing a solid material comprising at least bringing at least lithium sulfide, phosphorous sulfide, and a zinc 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.

The present application discloses a sulfide solid electrolyte and a method for the preparation thereof, an all solid state lithium secondary battery, and an apparatus containing the all solid state lithium secondary battery. The sulfide solid electrolyte is obtained by compounding at least Li.sub.2S, P.sub.2S.sub.5 and a dopant M.sub.xS.sub.2O.sub.3, wherein M is one or more selected from Na, K, Ba and Ca, and 1≤x≤2.

The invention relates to a highly reactive, high-purity, free-flowing and dust-free lithium sulfide powder having an average particle size between 250 and 1,500 μm and BET surface areas between 1 and 100 m.sup.2/g. The invention, furthermore, relates to a process for its preparation, wherein in a first step, lithium hydroxide monohydrate is heated in a temperature-controlled unit to a reaction temperature between 150° C. and 450° C. in the absence of air, and an inert gas is passed over or through it, until the residual water of crystallization content of the formed lithium hydroxide is less than 5 wt. % and in a second step, the anhydrous lithium hydroxide formed in the first step is mixed, overflowed or traversed by a gaseous sulfur source from the group consisting of hydrogen sulfide, elemental sulfur, carbon disulfide, mercaptans or sulfur nitrides.

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

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

Provided is a battery comprising a cathode, an anode, and an electrolyte layer. The electrolyte layer includes a first electrolyte layer and a second electrolyte layer. The first electrolyte layer includes a first solid electrolyte material. The second electrolyte layer includes a second solid electrolyte material which is a material different from the first solid electrolyte material. The first solid electrolyte material includes lithium, at least one kind selected from the group consisting of metalloid elements and metal elements other than lithium, and at least one kind selected from the group consisting of chlorine, bromine, and iodine. The first solid electrolyte material does not include sulfur.

A solid electrolyte: (compound A) a compound that has a crystal phase having an argyrodite-type crystal structure and that is represented by Li.sub.aPS.sub.bX.sub.c, where X is at least one elemental halogen, a represents a number of 3.0 or more and 6.0 or less, b represents a number of 3.5 or more and 4.8 or less, and c represents a number of 0.1 or more and 3.0 or less; and (compound B) a compound that is represented by LiX, where X is as defined above. The compound B has a crystallite size of 25 nm or more. The solid electrolyte preferably has a BET specific surface area of 14.0 m.sup.2/g or less.

The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and contains water generated during heating at 300° C. in Karl Fischer titration in an amount of 317.5 ppm by mass or less. Here, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.