Enhancing Low-Temperature Performance of Sodium-Ion Batteries via Anion-Solvent Interactions

Sodium-ion batteries (SIBs) exhibit better low-temperature electrochemical performance than lithium-ion batteries (LIBs) due to sodium's unique physical and chemical properties. However, SIBs face significant challenges at extremely low temperatures, such as -40 degrees C, where electrolyte salting out, reduced ionic conductivity, and increased viscosity hinder performance. Optimizing electrolyte formulations is critical to overcoming these issues. This study introduces 1,3-Dioxolane (DOL) as a co-solvent to enhance electrolyte performance under low-temperature conditions. DOL significantly improves NaPF6 solubility by forming strong interactions with anions. Additionally, it modifies the solvation structure, increasing anion participation and promoting the formation of a NaF-rich solid electrolyte interphase (SEI) on the anode surface. These enhancements are supported by experimental data and computational simulations. The addition of DOL also improves the cycling stability of commercial Sn microparticles (mu-Sn) at low temperatures. mu-Sn achieves a high reversible capacity of 248.3 mAh g(-1) at -40 degrees C after 1500 cycles at 0.5 A g(-1), significantly outperforming electrolytes without DOL. This work provides a novel approach for designing advanced low-temperature electrolytes, enabling more reliable sodium-ion battery performance in extreme environments.