A solid electrolyte contains at least elemental lithium (Li), elemental phosphorus (P), elemental sulfur (S), elemental halogen (X), and elemental oxygen (O), and has a crystalline phase with an argyrodite-type crystal structure. In the solid electrolyte, the molar ratio of the elemental halogen (X) to the elemental phosphorus (P), X/P, is more than 1.0 and less than 2.4, and the molar ratio of the elemental oxygen (O) to the elemental phosphorus (P), O/P, is more than 0 and less than 0.5. In an X-ray diffraction pattern, the solid electrolyte exhibits: peak A in the range of 2θ=21.6° to 22.6°, peak B in the range of 2θ=22.7° to 23.7°; and peak C in the range of 2θ=35.8° to 36.8°, the X-ray diffraction pattern being obtained by an X-ray diffractometer (XRD) using CuKα1 radiation.

An electrochemical device includes a positive electrode, a negative electrode, and an electrolyte having lithium ion conductivity. The positive electrode includes a positive current collector and a positive electrode mixture layer supported on the positive current collector. The positive electrode mixture layer contains a positive electrode active material reversibly doped with an anion. The negative electrode includes a negative current collector and a negative electrode mixture layer supported on the negative current collector. The negative electrode mixture layer contains a negative electrode active material reversibly doped with lithium ions. The negative electrode active material contains non-graphitizable carbon. A ratio Mp/Mn of a mass Mp of the positive electrode active material supported on a unit area of the positive electrode to a mass Mn of the negative electrode active material supported on a unit area of the negative electrode is in a range from 1.1 to 2.5, inclusive.

An electrochemical device includes a positive electrode, a negative electrode, and an electrolyte having lithium ion conductivity. The positive electrode includes a positive current collector and a positive electrode mixture layer supported on the positive current collector. The positive electrode mixture layer contains a positive electrode active material reversibly doped with an anion. The negative electrode includes a negative current collector and a negative electrode mixture layer supported on the negative current collector. The negative electrode mixture layer contains a negative electrode active material reversibly doped with lithium ions. The negative electrode active material contains non-graphitizable carbon. A ratio Mp/Mn of a mass Mp of the positive electrode active material supported on a unit area of the positive electrode to a mass Mn of the negative electrode active material supported on a unit area of the negative electrode is in a range from 1.1 to 2.5, inclusive.

Disclosed is a positive electrode material having inhibited increase in heat release when exposed to high temperature. The positive electrode material of the disclosure comprises a positive electrode active material, a first solid electrolyte and a second solid electrolyte, wherein the positive electrode active material comprises a lithium-containing oxide, the first solid electrolyte comprises Li and X as constituent elements and comprises no S, X is one or more elements selected from the group consisting of F, Cl, Br and I, the second solid electrolyte comprises Li and S as constituent elements, the first solid electrolyte covers at least part of the surface of the positive electrode active material, the second solid electrolyte contacts with the positive electrode active material across the first solid electrolyte, and the average covering thickness of the first solid electrolyte is 104 nm or greater.

Disclosed is a positive electrode material having inhibited increase in heat release when exposed to high temperature. The positive electrode material of the disclosure comprises a positive electrode active material, a first solid electrolyte and a second solid electrolyte, wherein the positive electrode active material comprises a lithium-containing oxide, the first solid electrolyte comprises Li and X as constituent elements and comprises no S, X is one or more elements selected from the group consisting of F, Cl, Br and I, the second solid electrolyte comprises Li and S as constituent elements, the first solid electrolyte covers at least part of the surface of the positive electrode active material, the second solid electrolyte contacts with the positive electrode active material across the first solid electrolyte, and the average covering thickness of the first solid electrolyte is 104 nm or greater.

An all-solid-state secondary battery mixture, a secondary battery electrode mixture sheet containing the all-solid-state secondary battery mixture, and a secondary battery including the all-solid-state secondary battery sheet. Also provided is a method for producing an all-solid-state secondary battery sheet containing a polytetrafluoroethylene resin having a fine fiber structure. The all-solid-state secondary battery mixture includes a solid-state electrolyte and a binder. The binder is a polytetrafluoroethylene resin, and the polytetrafluoroethylene resin has a fibrous structure with a fibril diameter (median value) of 70 nm or less. In addition, the all-solid-state secondary battery mixture sheet contains the all-solid-state secondary battery mixture.

A unit stack-cell structure and an all-solid-state secondary battery including the same, the unit stack-cell structure includes a plurality of stacked unit cells, each unit cell of the plurality of stacked unit cells including a laminate in which a cathode layer; a solid electrolyte layer; an anode layer; and an elastic layer are sequentially arranged, wherein the elastic layer has a compressive strength of greater than or equal to about 0.28 MPa and less than about 0.6 MPa in a compressibility interval in a range of about 40% to about 70%.

A unit stack-cell structure and an all-solid-state secondary battery including the same, the unit stack-cell structure includes a plurality of stacked unit cells, each unit cell of the plurality of stacked unit cells including a laminate in which a cathode layer; a solid electrolyte layer; an anode layer; and an elastic layer are sequentially arranged, wherein the elastic layer has a compressive strength of greater than or equal to about 0.28 MPa and less than about 0.6 MPa in a compressibility interval in a range of about 40% to about 70%.

An electrode layer for an all-solid state battery contains an electrode active material, a sulfide solid electrolyte, and a residual liquid, where the residual liquid has a δ.sub.P of less than 2.9 MPa.sup.½ in a Hansen solubility parameter and a boiling point of 190° C. or higher.

An electrode layer for an all-solid state battery contains an electrode active material, a sulfide solid electrolyte, and a residual liquid, where the residual liquid has a δ.sub.P of less than 2.9 MPa.sup.½ in a Hansen solubility parameter and a boiling point of 190° C. or higher.