Interfacial Chemistry of Perfluorinated-Anion Additives Deciphering Ether-Based Electrolytes for Sodium-Ion Batteries

Ether-based electrolytes with high reductive stability can be compatible with multiple anodes. However, their low oxidative stability and low flash point lead to restrictions for sodium-ion batteries. Here we report a rational coupling design between perfluorinated-anion additives and cathode/solvent to self-assemble a protective cathode-electrolyte interphase (CEI) and concurrently build a −C–F···H–C– stable interaction network to promote the stability of ethers. The preferential adsorption and oxidization of additives enable the electrolyte to restrain weak oxidation at low voltage and withstand high voltage up to 4.5 V vs Na/Na+. Such additives also facilitate uniform Na deposition and inhibit the growth of Na dendrites. The weak −C–F···H–C– pseudo hydrogen bond developed between additives and solvents contributes to the markedly elevated thermal stability of the electrolyte up to 60 °C. These results highlight the significance of regulating the interfacial environment and solvation effect by sacrificial additives for boosting the electrochemical and high-temperature performance.