Unveiling kinetic characteristics of the interface between solid electrolyte and cathode for all-solid-state fluoride ion batteries towards a wide-temperature application

All-solid-state fluoride ion batteries (FIBs) are regarded as promising candidates for post-lithium-ion energy storage systems due to their higher energy density, good safety and wide temperature tolerance. However, the operation of all-solid-state FIBs involves complex dynamic characteristics of the interface between electrolyte and electrode materials. Herin, the relevant dynamic characteristics of the interface taking beta-PbSnF4 electrolyte and BiF3 as cathode are elaborately studied. Based on the Alomd-West formula, it is found that the ionic conductivity of beta-PbSnF4 is more affected by the hopping frequency than the carrier concentration. Furthermore, solid/solid interface is critical for the smooth shuttle of F- ions, and it is proved that tuning the particle size of BiF3 can enhance F- ions transfer dynamic due to the enhanced interface compatibility between active materials and electrolytes. As a result, the assembled S-BiF3|beta-PbSnF4|Sn battery delivers a maximum discharge capacity of 175.9 mAh g(-1) at a current density of 40 mA g(-1) and remains a final capacity of 94.9 mAh g(-1) after 150 cycles at room temperature. Furthermore, S-BiF3|beta-PbSnF4|Sn battery also shows good high and low-temperature performance. The in-depth analysis of ion migration characteristics of electrolyte and the interface optimization provides a guideline for developing wide temperature range all-solid-state FIBs.