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. [Display omitted] • The challenges and design elements of SEI are summarized comprehensively. • The formation mechanism, characteristics, and failure mechanism of SEI are systematically reviewed. • The latest development of SEI regulation strategy is discussed. • The opportunity and research direction of interface design for long lasting sodium metal batteries are prospected. Inhomogeneous and fragile solid electrolyte interphase (SEI) leads to poor battery cycle life and safety hazards, which is a key challenge that limits the practical application of low-cost sodium metal anodes. Although sodium metal batteries based on non-aqueous liquid and solid electrolytes have made great progress in terms of interfacial chemistry and SEI regulation strategies, the relevant evaluation of SEI from the perspective of the electrolyte is not well understood. This paper reviews the formation mechanism, physicochemical properties, and failure mechanism of SEI at the interface between the sodium metal and the liquid/solid electrolyte, focusing on poor stability, compatibility, interfacial ion transport problems, and influencing factors. Recent advances in SEI regulation are summarized in terms of electrolytes, artificial interphases, and electrode engineering to achieve ideal electrochemical reversibility. The effectiveness of the SEI engineering strategies was evaluated based on a comprehensive review of the interfacial stability in different electrolyte systems. Finally, the challenges associated with rational interface design for long-lasting sodium metal batteries are discussed, along with promising avenues for the same. [ABSTRACT FROM AUTHOR]