Utilizing Weakly-Solvated Diglyme-Based Electrolyte to Achieve a 10000-Cycles Durable Na3V2(PO4)2F3 Cathode Endured at -20℃

The commercialization of sodium-ion batteries (SIBs) is tremendously limited as performance decline in extreme environments (such as below 0 ℃). This work proposes remarkable low-temperature (low-T) SIBs based on 0.5 M NaPF6 diglyme electrolyte. By a series of in-depth analysis, including XPS, temperature-dependent EIS, in- and ex-situ XRD, etc., finding that the weakly solvated structure of Na+-diglyme is beneficial to accelerating diffusivity of Na+ and reducing charge transfer energy (from 461.9 to 158.6 meV), which is effectively to ameliorate the low-T sodium storage mechanism. Moreover, The NaF-rich cathode electrolyte interphase (CEI) formed in diglyme is conducive to stabilize the interfacial structure and accelerate transport of Na+. All these merits collectively lead to high adaptability of low-concentration diglyme-based electrolyte to low-T. It has been verified that this system delivers 95.6% of room-temperature (RT) capacity, and full-cell delivers huge superiority in lifespan (working stably for 10,000 cycles) at − 20 ℃. Even at − 60 ℃, the battery still attains high capacity density (79.2 mAh g−1). These results provide new research ideas for improving the low-T performance of energy storage equipment.