Provided are a sodium ion-conductive crystal-containing solid electrolyte sheet capable of giving excellent battery characteristics even when reduced in thickness, and an all-solid-state battery using the same. The solid electrolyte sheet contains at least one type of sodium ion-conductive crystal selected from β″-alumina and NASICON crystal and has a thickness of 500 μm or less and a flatness of 200 μm or less.

The solid electrolyte material comprises Li, Y, X, and O, where X is one selected from the group consisting of F, Cl, Br, and I, and the molar ratio of O to Y is greater than 0.01 and less than 0.52.

The solid electrolyte material comprises Li, Y, X, O, and H, where X is one selected from the group consisting of F, Cl, Br, and I, and the molar ratio of O to Y is greater than 0.01 and less than 0.38.

A ceramic powder material containing: a first garnet-type compound containing Li, La, and Zr; and a second garnet-type compound containing Li, La, and Zr and having a composition different from a composition of the first garnet-type compound, in which the first garnet-type compound and the second garnet-type compound are represented by Formula [1] Li.sub.7-(3x+y)M1.sub.xLa.sub.3Zr.sub.2-yM2.sub.yO.sub.12, where Ml is Al or Ga, M2 is Nb or Ta, the first garnet-type compound satisfies 0≤(3x+y)≤0.5, and the second garnet-type compound satisfies 0.5<(3x+y)≤1.5.

A solid state battery that includes at least one battery constituent unit including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, wherein at least the solid electrolyte layer includes a plurality of solid electrolyte particles having a portion in which a constituent ratio of a transition metal element to all metal elements, excluding lithium, is 0.0% to 15%.

Provided are a composite oxide powder from which dense solid electrolyte objects having a high ion conductivity can be produced and a method for producing the composite oxide powder. The composite oxide powder is composed of particles comprising lithium (Li), lanthanum (La), zirconium (Zr), and oxygen (O) and having a cubic garnet-type crystal structure, and has a volume particle size distribution in which the 50% diameter (D50) is 1,000 nm or smaller, the composite oxide powder having a pyrochlore phase content of 10 mass % or less.

A solid ion conductor compound includes a compound represented by Formula 1:
Li.sub.6−wHf.sub.2−xM.sub.xO.sub.7−yZ.sub.y  Formula 1
where, in Formula 1, M is an element having an oxidation number of a and a is 5, 6, or a combination thereof, Z is an element having an oxidation number of −1, and 0<x<2, 0≤y≤2, and 0<w<6 and w=[(a−4)×x]+y.

A solid ion conductor compound includes a compound represented by Formula 1:
Li.sub.6−wHf.sub.2−xM.sub.xO.sub.7−yZ.sub.y  Formula 1
where, in Formula 1, M is an element having an oxidation number of a and a is 5, 6, or a combination thereof, Z is an element having an oxidation number of −1, and 0<x<2, 0≤y≤2, and 0<w<6 and w=[(a−4)×x]+y.

An electrochromic device according to an embodiment includes a first transparent conductive layer, an ion storage layer, an electrolyte layer, an electrochromic layer, and a second transparent conductive layer. The electrolyte layer includes a tantalum atom. The electrochromic layer includes a tungsten atom. The ion storage layer includes an iridium atom and a tantalum atom. The ion storage layer is hydrogenated in bleached state and the electrochromic device has a transmittance of 64.1% or more in bleached state. A difference between the transmittance of the electrochromic device in bleached state and the transmittance of the electrochromic device in colored state is 8.4% or more.

An electrochromic device according to an embodiment includes a first transparent conductive layer, an ion storage layer, an electrolyte layer, an electrochromic layer, and a second transparent conductive layer. The electrolyte layer includes a tantalum atom. The electrochromic layer includes a tungsten atom. The ion storage layer includes an iridium atom and a tantalum atom. The ion storage layer is hydrogenated in bleached state and the electrochromic device has a transmittance of 64.1% or more in bleached state. A difference between the transmittance of the electrochromic device in bleached state and the transmittance of the electrochromic device in colored state is 8.4% or more.