Provided are an inorganic solid electrolyte material including a sulfide-based inorganic solid electrolyte and an electron-insulating inorganic material that coats a surface of the sulfide-based inorganic solid electrolyte, is solid at 100° C., and fuses at a specific temperature, a slurry using the same, a solid electrolyte film for an all-solid state secondary battery, a solid electrolyte sheet for an all-solid state secondary battery, a positive electrode active material film for an all-solid state secondary battery, a negative electrode active material film for an all-solid state secondary battery, an electrode sheet for an all-solid state secondary battery, an all-solid state secondary battery, and a method for manufacturing an all-solid state secondary battery.

A hydrogel has water, a polyvinylsulfonic acid-based polymer, and a polymer matrix containing the water and the polyvinylsulfonic acid-based polymer, in which the polymer matrix contains a copolymer of a monofunctional monomer having one ethylenically unsaturated group and a polyfunctional monomer having 2 to 6 ethylenically unsaturated groups, the copolymer has a hydrophilic group binding to its main chain, the polymer matrix is contained in an amount of 2 to 80 parts by mass in 100 parts by mass of the hydrogel, a polymer derived from the polyfunctional monomer is contained in a proportion of 0.1 to 5 parts by mass in 100 parts by mass of the copolymer, the polyvinylsulfonic acid-based polymer is contained in an amount of 0.1 to 150 parts by mass in 100 parts by mass of the polymer matrix, and the polyvinylsulfonic acid-based polymer has a weight average molecular weight of 200,000 to 3,000,000.

A solid electrolyte material contains Li, Y, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, La, Sm, Bi, Zr, Hf, Nb, and Ta, and at least one selected from the group consisting of Cl, Br, and I. An X-ray diffraction pattern of the solid electrolyte material obtained by using Cu-Kα radiation as the X-ray source includes peaks within the range in which the diffraction angle 2θ is 25° or more and 35° or less, and also includes at least one peak within the range in which the diffraction angle 2θ is 43° or more and 51° or less.

A solid electrolyte material contains Li; Y; at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Zr, Nb, and Ta; and at least one selected from the group consisting of Cl, Br, and I. An X-ray diffraction pattern of the solid electrolyte material obtained using Cu—Kα radiation as an X-ray source includes peaks in a range of diffraction angles 2θ of 30° or more and 33° or less, in a range of diffraction angles 2θ of 39° or more and 43° or less, and in a range of diffraction angles 2θ of 47° or more and 51° or less.

A Li ion conductor includes a garnet-type composite metal oxide phase (L) containing Li, La, Zr, and O. The Li ion conductor has a diffraction peak at least one of at 2θ=13.8° ±1° and at 2θ=15.2° ±1° in X-ray diffraction measurement using CuKa rays. The Li ion conductor may have a metal-containing phase (K) different from the garnet-type composite metal oxide phase (L), and the metal-containing phase (K) contains a halogen element and Li.

A sulfide solid electrolyte is provided having peak A at 2θ=20.7°±0.5° in an X-ray diffraction pattern obtained by performing X-ray diffraction measurement using CuKα1 radiation. It is preferable that the sulfide solid electrolyte has peak B at 2θ=25.4°±1.0° in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement using CuKα1 radiation. It is also preferable that the value of the ratio of I.sub.A to I.sub.B, I.sub.A/I.sub.B, is more than 0 and 0.7 or less, where I.sub.A is the intensity of peak A and I.sub.B is the intensity of peak B. It is also preferable that the sulfide solid electrolyte has peak C at 2θ=22.0°±0.5° in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement using CuKα1 radiation.

A lithium ion conductive material has a composition formula of Li.sub.a(OH).sub.bF.sub.cCl.sub.dBr.sub.1-d, where 1.8≤a≤2.3, b=a −c−1, 0<c≤0.30, 0<d<1, and includes an antiperovskite-type crystal phase. The lithium ion conductive material is manufactured, for example, by heating LiOH, LiF, LiCl, and LiBr at a temperature not lower than 250° C. and not higher than 600° C. for 0.1 hours or more while stirring them at a molar ratio of 1:X:Y:Z (where 0.03≤X≤0.3, 0.2≤Y<1.1, 0<Z<1) under an Ar gas atmosphere.

A solid electrolyte composition includes a solvent and a solid electrolyte dispersed in the solvent. The solid electrolyte includes a halide solid electrolyte. The solvent has a polar component δp of Hansen solubility parameters that is greater than 0 and less than 5.9. The halide solid electrolyte contains Li, M1, and X1. M1 is at least one selected from the group consisting of metalloid elements and metal elements other than Li. X1 is at least one selected from the group consisting of F, Cl, Br, and I.

A solid electrolyte composition containing an inorganic solid electrolyte having conductivity of an ion of a metal belonging to Group I or II of the periodic table and an acid-modified cellulose nanofiber, a solid electrolyte-containing sheet and a manufacturing method therefor, and an all-solid state secondary battery having an inorganic solid electrolyte layer containing the inorganic solid electrolyte having conductivity of an ion of a metal belonging to Group I or II of the periodic table and an acid-modified cellulose nanofiber and a manufacturing method therefor.

A solid electrolyte material includes a first crystal phase. The first crystal phase has a composition that is deficient in Li as compared with a composition represented by the following composition formula (1).
Li.sub.3Y.sub.1Cl.sub.6  formula (1)