Intermolecular Attraction-Repulsion Forces Enable Self-Reinforcing Electrolytes for Wide-Temperature Sodium Metal Batteries

Developing an electrolyte system with stable performance over a wide temperature range is crucial for energy storage devices operating in extreme environments, especially achieving both simultaneously across a wide temperature range remains a major challenge. Here, a temperature-responsive electrolyte is proposed by the synergistic regulation of dipole-dipole attraction and electrostatic repulsion. Specifically, strong dipole-dipole attraction between cyclopentyl methyl ether (CPME) and tetrahydrofuran (THF) effectively constrains free THF molecules, thereby enhancing chemical stability at elevated temperatures. Simultaneously, the electrostatic repulsion between CPME and diethylene glycol dimethyl ether (DGM) strengthens anion participation at low temperatures (LT), forming a "temperature self-reinforcing" solvation structure that significantly improves LT desolvation kinetics. Consequently, the engineered electrolyte system maintains a Coulombic efficiency above 99.5% throughout the entire temperature range, remarkably reaching 99.9% at -20 °C and -40 °C. Furthermore, the Na||Na3V2(PO4)3 (NVP) full cell assembled with this electrolyte exhibited stable operation over 1200 cycles at -40 °C under a 2 C rate, retaining 97.2% of its initial capacity. Additionally, a 420 mAh pouch cell was assembled, which demonstrated stable cycling performance at LT. This work offers another approach for designing wide-temperature-range electrolytes, highlighting the critical role of attractive and repulsive forces between solvent molecules in shaping the solvation structure.