Current-Driven SEI and Near-Surface Structural and Chemical Evolution in Lithium Metal Batteries

Lithium metal batteries promise of exceptional energy density is hindered by unstable solid electrolyte interphases (SEIs), which are highly sensitive to electrolyte composition and operating current. While weakly solvating and localized high-concentration electrolytes (LHCE) have shown potential to stabilize the SEI, the influence of current density on SEI evolution remains insufficiently understood. In this work, we integrate a Hybrid Ab Initio Reactive (HAIR) atomistic simulation method for generating realistic SEI structures with a novel Ionic-Current–Electric-Field (ICEF) framework to predict current-dependent ion transport using ReaxFF molecular dynamics. We apply this approach to two ether-based LHCE electrolytes, with chemistry differing only by addition of a small amount of a weak solvent to one of them, but marked differences in solvation structures, SEI structure and morphologies, and interactions with incoming ions. Our simulations reveal that elevated current densities destabilize some SEI components and stabilize others, forming specific aggregate species in the near-surface layer for each type of electrolytes, and inducing asymmetric Li⁺ desolvation, potentially affecting lithium deposition morphology and Coulombic efficiency. These findings demonstrate a clear dependence of SEI and near-surface layer composition and stability on current density, underscoring the importance of current as a critical design parameter. This framework offers a pathway for rational electrolyte engineering aimed at achieving stable, high-rate lithium metal batteries.