Additive-free ester-based electrolyte for fast-charging and wide-temperature sodium-ion full batteries

An ideal electrolyte for fast-charging and wide-temperature sodium-ion batteries must simultaneously exhibit excellent intrinsic physicochemical properties, rapid interfacial kinetics, and superior interfacial stability, yet achieving synergistic optimization of these three characteristics remains a formidable technical challenge. Herein, a high-performance additive-free ester-based electrolyte is constructed via a cosolvent and dual-anion strategy to manipulate the solvation structure and interfacial chemistry. The incorporation of dimethyl sulfite and sodium difluoro(oxalate)borate reduces the involvement of solvent molecules in the primary solvation sheath, while synergistically constructing S/F/B inorganic-rich electrode–electrolyte interface with high Na + conductivity, thereby significantly boosting interfacial kinetics and stability. Therefore, the Prussian blue||hard carbon full cells exhibit excellent fast-charging performance and wide-temperature adaptability from –30 to 100 °C. More importantly, the Ah-level pouch cells with high mass loading electrodes achieve 85.1% capacity retention after 200 cycles at 55 °C, proving great practical value of this additive-free ester electrolyte.