Oxide electrolyte sintered body and method for producing the same

An oxide electrolyte sintered body,

• wherein the oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion-conducting oxide which comprises Li, H, at least one kind of element L selected from the group consisting of an alkaline-earth element and a lanthanoid element, and at least one kind of element M selected from the group consisting of a transition element that can be 6-coordinated with oxygen and elements belonging to the Groups 12 to 15, and which is represented by a general formula (Lix−3y−z,Ey,Hz)LαMβOγ (where E is at least one kind of element selected from the group consisting of Al, Ga, Fe and Si, 3≤x−3y−z≤7, 0≤y≤0.22, 0≤z≤2.8, 2.5≤α≤3.5, 1.5≤β≤2.5, and 11≤γ≤13);
• wherein a lithium-containing flux is present at grain boundary triple junctions between the crystal particles;
• and
• wherein the oxide electrolyte sintered body satisfies the following formula 1:
• Rgb/(Rb+Rgb)≤0.6 Formula 1:
• where Rb is an intragranular resistance value that is an ion conductivity resistance inside the crystal particles, and Rgb is a grain boundary resistance value that is an ion conductivity resistance on grain boundaries between the crystal particles, and
• wherein the lithium-containing flux is at least one kind of compound selected from the group consisting of LiNO3 and LiOH.