Utilizing weakly-solvated diglyme-based electrolyte to achieve a 10,000-cycles durable Na3V2(PO4)2F3 cathode endured at-20 °C

The commercialization of sodium-ion batteries (SIBs) is tremendously limited as performance decline in extreme environments (such as below 0 degrees C). 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 degrees C. Even at -60 degrees C, 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.

Automated summary

This study proposes a low-temperature sodium-ion battery based on a 0.5M NaPF6 diglyme electrolyte. The weakly solvated structure of Na+-diglyme accelerates the diffusion of Na+ and reduces charge transfer energy, improving the low-temperature sodium storage mechanism. The system exhibits high adaptability to low temperatures and delivers stable performance even at extreme cold temperatures.