Ion–Dipole Interactions Modulated Anion-Reinforced Solvation Chemistry for Advanced Wide-Temperature Sodium-Ion Full Batteries

Wide-temperature sodium-ion batteries (SIBs) are considered promising candidates for large-scale energy storage systems under extreme temperature conditions. However, SIBs generally suffer from an unstable electrode–electrolyte interface (EEI) at high temperature and sluggish interfacial kinetics at low temperature, resulting in poor temperature tolerance with fast capacity degradation. Herein, a weakly coordinated carboxylate ester cosolvent, methyl butyrate, is employed to modulate the ion–dipole interactions in fluorine-free ester-based electrolyte for the anion-reinforced solvation chemistry. The unique solvent chemistry enables the construction of stable anion-derived inorganic-rich EEI on both cathode and anode surfaces while simultaneously reducing the desolvation energy barrier, thereby significantly enhancing the interfacial stability and kinetics. Therefore, the Prussian blue||hard carbon (PB||HC) full cell demonstrates a stable operation at a wide temperature range from −20 to 100 °C. Noticeably, the PB||HC 18650 cylindrical cell delivers a superior capacity retention of 91.41% after 230 cycles at an elevated temperature of 55 °C. This work provides valuable guidance for designing fluorine-free ester-based electrolytes through rational modulation of ion–dipole interactions, paving a promising pathway for wide-temperature sodium-ion full batteries.