Research progress on LT performance of sodium-ion battery electrolytes

Sodium-ion batteries (SIBs) have gained attention for their low cost and abundant sodium resources. However, at low temperature (LT), their electrolytes suffer from reduced conductivity, higher viscosity, poor interfacial stability, and sluggish ion transport, leading to capacity loss and shortened cycle life. These problems significantly restrict the practical application of SIBs in harsh or LT environments, where performance degradation, capacity fading, or even complete failure can occur. Therefore, enhancing the LT performance of SIB electrolytes has become a key research focus. Improvements in electrolyte formulation-including solvent selection, sodium salt optimization, and functional additive engineering-play a vital role in addressing issues such as ion transport limitations and unstable electrode-electrolyte interfaces at LT. This review provides a comprehensive summary of the strategies developed to optimize various types of SIB electrolytes under LT conditions, including organic solvent systems, ionic liquids, solid-state electrolytes, and co-solvents. In addition, it discusses the latest research progress, highlights representative studies, and outlines potential directions for future development, with the aim of guiding the design of high-performance SIBs for LT.