Implications of Na-ion solvation on Na anode–electrolyte interphase

Sodium-metal anode battery technologies have revolutionized energy storage research. In recent years, new insights have been gained regarding the solid electrolyte interphase (SEI) on a sodium-metal anode; however, several questions remain to be answered, in particular the impact of electrolyte structure on the composition and physicochemical stability of the SEI. In addition, the impact of ion-solvation chemistry on the crystallinity of the SEI warrants a more detailed understanding. This review discusses the crucial aspects of sodium-ion solvation chemistry and its impact on the stability of the SEI. The core principles guiding the design of electrolytes through additives, ion–solvent interaction, and ion-pair formation are highlighted. Future research directions necessary to design a stable sodium-metal anode are also discussed.