Solvation engineering of non-aqueous electrolytes for room-temperature fluoride-ion batteries

Fluoride-ion batteries (FIBs) with high energy density and low cost are a promising new generation battery system for renewable energy storage. However, their room-temperature operation is strongly impeded by the lack of compatible electrolytes. Herein, we demonstrate that a stable room-temperature FIB can be achieved by tailoring the solvation chemistry of a non-aqueous liquid electrolyte. As validated by computational modeling and spectroscopic investigations, the cost-efficient β-hydrogen-free tetramethylammonium fluoride (TMAF) salt can efficiently prevent Hofmann elimination-induced electrolyte decomposition. Meanwhile, the synergistic effect of strong-polarity solvent and anion acceptor additive endows the high salt solubility (up to 0.7 M) and room-temperature ionic conductivity (6.12×10−3 S cm−1 at 25°C) for the electrolyte. Owing to the virtue of this new electrolyte design, the Zn||CuF2 and Li||CuF2 FIBs were successfully constructed, delivering high reversibility, stable interface, and extended life. This work offers a new pathway for clearing the formidable bottlenecks in developing high-performance Fluoride-ion batteries.