Provided are plastic crystal-type solid electrolyte having high ion conductivity and a power storage device using the solid electrolyte. The solid electrolyte contains a plastic crystal doped with an electrolyte. The plastic crystal contains two or more types of cations in total, at least one of which is selected from the group of imidazoliums and quaternary ammoniums.

A sulfide solid electrolyte that contains lithium, phosphorus, sulfur, chlorine and bromine, wherein in powder X-ray diffraction analysis using CuKα rays, it has a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 2θ=29.7±0.5 deg, the diffraction peak A and the diffraction peak B satisfy the following formula (A), and a molar ratio of the chlorine to the phosphorus “c (Cl/P)” and a molar ratio of the bromine to the phosphorus “d (Br/P)” satisfies the following formula (1):
1.2<c+d<1.9  (1)
0.845<S.sub.A/S.sub.B<1.200  (A) where S.sub.A is an area of the diffraction peak A and S.sub.B is an area of the diffraction peak B.

A sulfide solid electrolyte that contains lithium, phosphorus, sulfur, chlorine and bromine, wherein in powder X-ray diffraction analysis using CuKα rays, it has a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 2θ=29.7±0.5 deg, the diffraction peak A and the diffraction peak B satisfy the following formula (A), and a molar ratio of the chlorine to the phosphorus “c (Cl/P)” and a molar ratio of the bromine to the phosphorus “d (Br/P)” satisfies the following formula (1):
1.2<c+d<1.9  (1)
0.845<S.sub.A/S.sub.B<1.200  (A) where S.sub.A is an area of the diffraction peak A and S.sub.B is an area of the diffraction peak B.

Provided is a novel solid electrolyte material of high density and high ionic conductivity, and an all-solid-state lithium ion secondary battery that utilizes the solid electrolyte material. The solid electrolyte material has a chemical composition represented by Li.sub.7-3xGa.sub.xLa.sub.3Zr.sub.2O.sub.12 (0.08≤x<0.5), has a relative density of 99% or higher, belongs to space group I-43d, in the cubic system, and has a garnet-type structure. The lithium ion conductivity of the solid electrolyte material is 2.0×10.sup.−3 S/cm or higher. The solid electrolyte material has a lattice constant a such that 1.29 nm≤a≤1.30 nm, and lithium ions occupy the 12a site, the 12b site and two types of 48e site, and gallium occupies the 12a site and the 12b site, in the crystal structure. The all-solid-state lithium ion secondary battery has a positive electrode, a negative electrode, and a solid electrolyte. The solid electrolyte is made up of the solid electrolyte material of the present invention.

A solid electrolyte composition containing a sulfide-based solid electrolyte having conductivity of ions of metals belonging to Group I or II of the periodic table, a binder, and a dispersion medium, in which an amount of dissolved oxygen in the solid electrolyte composition is 20 ppm or less, a manufacturing method thereof, a storage method thereof, and a kit thereof, a solid electrolyte-containing sheet having a layer made of the solid electrolyte composition, a storage method thereof, and a kit thereof, and an all-solid state secondary battery.

A solid electrolyte material of the present disclosure includes Li, M1, M2, and X. The M1 is at least one element selected from the group consisting of a group 2 element and a group 12 element. The M2 is at least three elements selected from the group consisting of a rare-earth element and a group 13 element. The X is at least one selected from the group consisting of F, Cl, Br, and I. A battery of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer includes the solid electrolyte material of the present disclosure.

A solid electrolyte material of the present disclosure consists of Li, M1, M2, and X. The M1 is one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. The M2 is at least one selected from the group consisting of Gd and Sm. The X is at least one selected from the group consisting of F, Cl, Br, and I. A battery of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer includes the solid electrolyte material of the present disclosure.

A nanoplatelet including a two-dimensional template including a first semiconductor nanocrystal; and a first shell including a second semiconductor nanocrystal disposed on a surface of the two-dimensional template, the second semiconductor nanocrystal having a composition different from the first semiconductor nanocrystal, wherein the second semiconductor nanocrystal includes a Group III-V compound, and wherein the nanoplatelet does not include cadmium.

A nanoplatelet including a two-dimensional template including a first semiconductor nanocrystal; and a first shell including a second semiconductor nanocrystal disposed on a surface of the two-dimensional template, the second semiconductor nanocrystal having a composition different from the first semiconductor nanocrystal, wherein the second semiconductor nanocrystal includes a Group III-V compound, and wherein the nanoplatelet does not include cadmium.

A sulfide solid electrolyte may include lithium, phosphorus and sulfur, and the sulfide solid electrolyte may have a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 29.7±0.5 deg in powder X-ray diffraction using CuKα rays, and a crystallite diameter in a range of from 5 to 20 nm.