Synthesis of Fast Fluoride-Ion-Conductive Fluorite-Type BaSb F (0.1 ≤ x ≤ 0.4): A Potential Solid Electrolyte for Fluoride-Ion Batteries.

Toward the development of high-performance solid electrolytes for fluoride-ion batteries, fluorite-type nanostructured solid solutions of BaSb F ( x ≤ 0.4) were synthesized by high-energy ball-milling method. Substitution of divalent Ba by trivalent Sb leads to an increase in interstitial fluoride-ion concentration, which enhances the ionic conductivity of the BaSb F (0.1 ≤ x ≤ 0.4) system. Total ionic conductivities of 4.4 × 10 and 3.9 × 10 S cm were obtained for BaSbF and BaSbF compositions at 160 °C, respectively. In comparison to isostructural BaLaF, the ionic conductivity of BaSbF is significantly higher, which is attributed to the presence of an electron lone pair on Sb. Introduction of such lone pairs seems to increase fluoride-ion mobility in solid solutions. In addition, BaSbF was tested as a cathode material against Ce and Zn anode using LaBaF as the electrolyte. BaSbF/LaBaF/Ce cell showed high discharge and charge capacities of 301 and 170 mA h g, respectively, in the first cycle at 150 °C.