Status and strategies of electrolyte engineering for low-temperature sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted extensive attention owing to their advantages of abundant sodium reserves, excellent low-temperature performance, low cost and high safety compared with the widely used lithium-ion batteries. However, the application of sodium-ion batteries at extreme low temperatures is severely limited due to the increase in the electrolyte viscosity, stability of the solid electrolyte interphase (SEI), and increase in the de-solvation energy for the sodium ions (Na+). Thus, it is urgent to design novel electrolytes that can operate at freezing temperature for the further promotion and enhanced adaptability of sodium ion batteries in extreme low-temperature environments. Herein, we summarize the development of low-temperature electrolytes for sodium ion batteries based on the following components: co-solvents, sodium salts, and additives, and then propose several general strategies for the preparation of electrolytes to provide guidance for the systematic design and further commercial application of low-temperature electrolytes for SIBs. Herein, we summarize the development of low-temperature electrolyte engineering for SIBs, and then propose several strategies to provide guidance for the systematic design and further commercial application of low-temperature SIBs.