Lithium ion-conducting garnet type oxide
An oxide-based solid electrolyte with a high lithium ion conductance is provided. A lithium ion-conducting garnet type oxide includes Li, La, Ga, Zr, a halogen element, and oxygen. A lithium ion conductivity at room temperature is not lower than 1.0×10 −3 S/cm. A proportion of Ga with respect to 1 mole of the oxide may be not larger than 0.5 moles. The halogen element may be at least one type selected from the group consisting of Cl, Br, and I, and a proportion of Li with respect to 1 mole of the oxide may be not smaller than 6.1 moles and smaller than 6.5 moles.
1 . A lithium ion-conducting garnet type oxide comprising:
Li;
La;
Ga;
Zr;
a halogen element; and
oxygen,
wherein a lithium ion conductivity at room temperature is not lower than 1.0×10 −3 S/cm,
wherein the halogen element is Cl, and
wherein a halogen concentration C Cl (7 nm) in terms of atomic % at a position at a depth of 7 nm from a surface of the lithium ion-conducting garnet type oxide is larger than a halogen concentration C Cl (surface) in terms of atomic % at the surface of the lithium ion-conducting garnet type oxide, and a halogen concentration C Cl (43 nm) in terms of atomic % at a position at a depth of 43 nm from the surface of the lithium ion-conducting garnet type oxide is larger than the halogen concentration C Cl (7 nm) in terms of atomic %.
2 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein a proportion of Ga with respect to 1 mole of the lithium ion-conducting garnet type oxide is not larger than 0.5 moles.
3 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein a proportion of Li with respect to 1 mole of the lithium ion-conducting garnet type oxide is not smaller than 6.1 moles and smaller than 6.5 moles.
4 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein a proportion of Cl with respect to a total of all elements constituting the lithium ion-conducting garnet type oxide is not higher than 0.20 atom %.
5 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein a lattice constant is not smaller than 12.98 Å.
6 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein a relative density is not lower than 75%.
7 . The lithium ion-conducting garnet type oxide according to claim 1 , wherein
the halogen concentration C Cl (7 nm) in terms of atomic % at the position at the depth of 7 nm from the surface of the lithium ion-conducting garnet type oxide is not smaller than 5 times and not larger than 13 times the halogen concentration C Cl (surface) in terms of atomic % at the surface of the lithium ion-conducting garnet type oxide, and
the halogen concentration C Cl (43 nm) in terms of atomic % at the position at the depth of 43 nm from the surface of the lithium ion-conducting garnet type oxide is not smaller than 1.5 times and not larger than 4 times the halogen concentration C Cl (7 nm) in terms of atomic % at the position at the depth of 7 nm from the surface of the lithium ion-conducting garnet type oxide.