Research progress of solid electrolyte interphase for sodium metal anodes

The limited stability, compatibility, and ion transport capacity of SEI remain key challenges in the development of high-energy–density sodium metal batteries. In order to realize the rational design and facile synthesis of SEI, the influencing factors of different challenges were systematically sorted out. By improving SEI chemical/electrochemical stability, mechanical stability, and thermal stability, the voltage window and temperature range of the battery operation can be effectively broadened. Suppressing the volume effect, phase exfoliation, and phase dissolution to enhance SEI compatibility is crucial for extending battery cycle life. The stability of ion transport at the electrode–electrolyte interface is affected by the composition, structure, and homogeneity of the interfacial phase, and fast and uniform interfacial Na+ transport can enable high-rate, high-safety sodium ion battery designs.