| Abstract Scope |
The development of high-performance fluoride-ion conductors is essential for realizing all-solid-state fluoride-ion batteries with high theoretical energy density. However, currently known materials rarely combine a wide electrochemical stability window and sufficient ionic conductivity near room temperature. Improving conductivity is also challenging, because introducing defects or extra carriers often destabilizes the crystal framework. These limitations highlight the need for new design strategies.
In this study, we explored a new class of layered fluorosulfides as fluoride-ion conductors. Their anion-ordered layered structures enable two-dimensional fluoride-ion migration. We found that ionic transport in these fluorosulfides is strongly affected by the local cation arrangement and adjacent layers. By tuning the composition, the conductivity was improved to a level comparable to leading fluoride-ion conductors. In addition, these fluorosulfides showed high vacancy tolerance without losing structural integrity, suggesting a flexible framework that accommodates defect formation while maintaining fast ionic transport. |