A Growing Appreciation for the Role of LiF in the Solid Electrolyte Interphase

Abstract Rechargeable lithium batteries (RLBs) have revolutionized energy storage technology. However, short lifetime and safety issues have hampered their further commercialization, which is mainly attributable to the unstable solid‐electrolyte interphase (SEI) and uncontrolled lithium dendrite growth. In recent years, research on SEI has been pursued with determination worldwide. However, the structure and composition of the SEI have long been debated. Especially, the role of the main component, LiF, remains elusive. In this review, the structure and composition of SEIs are focused upon and the role of LiF in SEI is further analyzed. To this end, first, the development history of the SEI model is recounted. Second, the fundamental understanding of SEI is recalled. Third, the anode materials that can generate LiF in the SEI are categorized and discussed. Fourth, the characterization techniques of SEI layers are introduced. Fifth, the transport mechanism of Li + ions within the SEI is discussed. Sixth, the physical properties of LiF are revisited. Seventh, the source of LiF is deeply analyzed. Finally, general conclusions and a perspective on the future research directions for SEI that may promote the large‐scale applications of lithium metal batteries is discussed.