Underlying Mechanism of Electrolyte Compositional Engineering Based on Additive Solvation‐Structure Governing Solid Electrolyte Interphase Formation in Lithium‐Ion Batteries

Abstract Substantial efforts are dedicated to optimizing the additive dosage in the electrolyte and studying its effect on solid electrolyte interphase (SEI) formation in Li‐ion batteries (LIBs). This study reveals that the decomposition characteristics of the additive based on its lithium‐ion solvation nature significantly contribute to controlling SEI formation. During SEI formation, the strong lithium‐ion solvating additive spontaneously migrates to the negative electrode due to negative charge accumulation on the surface, and SEI reinforcement is feasible by increasing the additive dosage. In contrast, population‐based SEI formation occurs with a weaker solvating additive, so dosage‐dependent modification of the SEI is not effective. These findings demonstrate that compositional electrolyte engineering based on the solvation properties of the additive can be more effective than empirical and experimental studies based on trial and error.