Research progress of electrolyte additives for subzero-temperature aqueous sodium-ion batteries

Sodium-ion batteries are considered one of the perspective alternatives to lithium-ion batteries due to their affordability and plentiful supply of sodium. However, traditional sodium-ion batteries that use organic electrolytes pose a threat to public safety and the ecological environment. As a result, aqueous electrolytes with high safety and cost-effectiveness are becoming more popular. Unfortunately, typically aqueous electrolytes face limitations in ionic conductivity and have relatively high freezing points, which hinder their ability to function at extremely low temperatures. These issues can be resolved with an easy-to-use method called electrolyte additive. The research on electrolyte additives for subzero-temperature aqueous sodium-ion batteries has not been systematically reviewed at present. This review aims to provide a comprehensive summary of the electrolyte additives for subzero-temperature aqueous sodium-ion batteries. Furthermore, the potential development paths of electrolyte additives to promote the advancement of electrochemical energy storage are also explored. Graphical Abstract: (Figure presented.).