Unveiling the Role of Ion Pairs in Determining Electrolyte Stability and Solid Electrolyte Interphase Formation in Lithium Metal Batteries

Interface engineering (IE) has emerged as a promising strategy to address the challenges related to the high reactivity of Li-metal anodes in Li metal batteries (LMBs). A deeper understanding of the mechanism and kinetics of electrolyte decomposition on the electrode surface, which leads to the formation of the solid electrolyte interphase (SEI), is essential, as the SEI plays a crucial role in determining battery performance. Herein, we employed ab initio molecular dynamics simulations to study the role of the electrolyte structure and ion–solvent interactions, especially the effect of contact ion pairs (IPs) and solvent-separated IPs, which our simulations identified to be present in most of the electrolytes, in determining the structure and the dynamical formation of SEI. In addition to providing fundamental insights into SEI formation in LMBs, the results of this study will be useful in designing strategies to enhance electrolyte stability and tailor the composition of SEI.