Fluorine‐Free Hybrid Ether‐Ester Electrolyte for High‐Temperature Sodium‐Ion Full Batteries

ABSTRACT Ether‐based electrolytes have attracted extensive attention in the field of sodium‐ion batteries (SIBs) due to their excellent compatibility with anode materials. However, they suffer from unsatisfactory interfacial stability at elevated operation temperatures, which results in rapid capacity degradation. Herein, we successfully constructed a fluorine‐free hybrid ether‐ester electrolyte for high‐temperature SIBs by employing commercial linear carbonates esters to regulate the electrolyte solvation chemistry. The introduction of carbonate esters can effectively modulate the ion‐dipole interactions within the system, facilitating the formation of an anion‐enhanced solvation structure with low desolvation energy. In addition, this unique solvation structure can induce the formation of a stable electrode‐electrolyte interphase rich in inorganic components, which efficiently suppresses continuous electrolyte decomposition, transition metal dissolution, and irreversible phase transition of electrode materials. Consequently, the Prussian blue||hard carbon full cell exhibits outstanding electrochemical performance over a wide temperature range of 25°C–80°C, retaining 80.6% of its initial capacity after 300 cycles at 55°C. More importantly, the Ah‐level pouch cell delivers excellent electrochemical performance at both 25°C and 55°C, which further verifies the practical application potential of the fluorine‐free hybrid ether‐ester electrolyte and provides a feasible route for the application of ether‐based solvents in SIBs under high‐temperature scenarios.