Over the past two decades, the solid–electrolyte interphase (SEI) layer that forms on an electrode’s surface has been believed to be pivotal for stabilizing the electrode’s performance in lithium-ion batteries (LIBs). However, more and more researchers currently are realizing that the metal-ion solvation structure (e.g., Li+) in electrolytes and the derived interfacial model (i.e., the desolvation process) can affect the electrode’s performance significantly. Thus, herein we summarize recent research focused on how to discover the importance of an electrolyte’s solvation structure, develop a quantitative model to describe the solvation structure, construct an interfacial model to understand the electrode’s performance, and apply these theories to the design of electrolytes. We provide a timely review on the scientific relationship between the molecular interactions of metal ions, anions, and solvents in the interfacial model and the electrode’s performance, of which the viewpoint differs from the SEI interpretations before. These discoveries may herald a new, post-SEI era due to their significance for guiding the design of LIBs and their performance improvement, as well as developing other metal-ion batteries and beyond.

High-voltage lithium-ion batteries (HV-LIBs) enabled by high voltage electrolytes can effectively boost the energy density and power density, of which critical requirements to achieve long travel-distance, fast-charging, and reliable safety performances for electric vehicles. However, operating the batteries beyond the typical conditions of LIBs (4.3 V vs.Li/Li + ) leads to a severe electrolyte decomposition, while the interfacial side reactions remain elusive. These critical issues become the bottleneck for developing electrolytes for applications