Cycling degradation and safety issues in sodium-ion batteries: Promises of electrolyte additives

Sodium-ion batteries (SIBs) have drawn particular attention in recent years as a promising alternative to lithium-ion batteries (LIBs) due to the advantages of sodium (Na) metal. Like LIBs, SIBs suffer from deterioration of cycling performance due to reactions occurring at the electrode-electrolyte interfaces. Moreover, they encounter safety issues arising from conventional organic electrolytes' flammability and the abuse of battery under overcharge conditions. Adding a small dose of additives into the electrolyte of SIBs can positively mitigate the abovementioned problems. In addition to categorizing the electrolyte additives used in SIBs, the recently published research and results on applying electrolyte additives in SIBs are comprehensively evaluated in this review paper. The challenges associated with the development of SIBs in terms of their electrolyte and the practical suggestion for exploring new electrolyte additives special to SIBs are thoroughly discussed.