Synthesis and characterization of Ca(1−x)SmxF(2+x) (0 ≤ x ≤ 0.15) solid electrolytes for fluoride-ion batteries

Abstract

Calcium fluoride solid electrolytes have been identified as a candidate for solid-state fluoride-ion batteries (FIBs). Here, we investigate the doping of CaF₂ with samarium — Ca_1−xSm_xF_2+x (0 ≤ x ≤ 0.15) — obtained by solid synthesis via high-energy ball milling. Structural, morphological, and ionic conductivity studies of the as-prepared materials were examined. It reveals that the fluorite-type structure is dominating with a crystallite size of 12–14 nm. The highest ionic conductivity at room temperature had been obtained for Ca_0.95Sm_0.05F_2.95 with a value of 2.8 × 10⁻⁶ S·cm⁻¹. It proves that a small content of Sm doping can considerably improve the ionic conductivity of CaF₂.