Varied solvent-solvent interactions in hybrid-based electrolytes boost sodium ion transport kinetics at low temperature

XY Qiao and RY Wang and JQ Li and T Chen and ZZ Li and FQR Guo and RX Wang and YX Chen and ZG Wu and XD Guo, CHEMICAL ENGINEERING JOURNAL, 519, 164777 (2025).

DOI: 10.1016/j.cej.2025.164777

The high viscosity and low ionic conductivity of organic electrolytes at low temperature (LT) are critical factors affecting the performance of sodium-ion batteries (SIBs), significantly reducing Na+ migration rates and leading to sluggish kinetics. Previous studies have indicated that while propylene carbonate (PC) solvents exhibit widetemperature properties, but their high viscosity at LT limits its applicability. To address this limitation, we have designed a low-viscosity hybrid ester- ether electrolyte that harnesses the solvent-solvent interactions. Through their distinct solvation behaviors, whether THF and ES participate in the construction of the solvation structure, they synergistically reduce the solvation effects of PC. It has been established that THF actively participates in the formation of the solvation structure, while ES remains excluded from the solvation shell. The competitive synergistic effect exhibited by THF and ES effectively not only reduce viscosity but also boosts ion transport kinetics at LT conditions. The initial capacity of the NVP//Na battery at 0.5C is 91 mAh g-1 at -20 degrees C, delivers a stable capacity retention rate of 98% after 800 cycles. The initial discharge capacity is 80 mAh g-1 at -40 degrees C, and the capacity retention is 78% at 100 cycles. This study of the regulation of the solvation structure through solventsolvent interaction provides new insight for the design of LT electrolytes.

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