Fundamentals and perspectives of electrolyte additives for non-aqueous Na-ion batteries

Despite extensive research efforts to develop non-aqueous sodium-ion batteries (SIBs) as alternatives to lithium-based energy storage battery systems, their performance is still hindered by electrode-electrolyte side reactions. As a feasible strategy, the engineering of electrolyte additives has been regarded as one of the effective ways to address these critical problems. In this review, we provide a comprehensive overview of recent progress in electrolyte additives for non-aqueous SIBs. We classify the additives based on their effects on specific electrode materials and discuss the functions and mechanisms of each additive category. Finally, we propose future directions for electrolyte additive research, including studies on additives for improving cell performance under extreme conditions, optimizing electrolyte additive combinations, understanding the effect of additives on cathode-anode interactions, and understanding the characteristics of electrolyte additives.