Precisely deciphering solid electrolyte interphase

Solid electrolyte interphase (SEI) plays a critical role in the cycling stability and safety issues of rechargeable batteries. To provide valuable suggestions for customized SEI regulation, a precise SEI understanding is essential and advanced detection techniques are indispensable. In this review, SEI formation, structure, ion transport, and failure mechanisms were first elucidated from the fundamental perspectives. Emerging detection techniques were briefly introduced, according to the high demands of SEI deciphering in high sensitivity, visualization, quantification, and simulation. Then, emphasis was given to the current advances of SEI study, to provide a systematic cognition of SEI in the aspects of component identification, structural distribution, physical-chemical properties, SEI functionalities (including ion conductivity and electronic insulation), and SEI chemistry-structure-property relationship. In the future, more efforts are suggested to penetrate into basic scientific issues, dynamic processes, multi-technique integration, and simulational techniques to provide more reliable understanding and guidance of high-quality SEI.