Unraveling Li Desolvation on Solid Electrolyte Interphase by Ab Initio Metadynamics.

Abstract

Desolvation is an important step before the solvated ions can intercalate into the electrode material. This interfacial process involves different desolvation stages, physical phases, and intertwined kinetics and thermodynamics. Thus, the impacts of solid electrolyte interphase (SEI) components on Li⁺ desolvation remain poorly understood at a molecular scale though conventional simulations strive to accurately capture complex interfacial electronic interactions during desolvation. We hereby combined ab initio molecular dynamics (AIMD) and stepwise multisubphase space metadynamics to unravel Li⁺ desolvation and redox stability on common SEI components, LiF, Li₂CO₃, and lithium ethylene monocarbonate (LEMC). Desolvation energy barriers were found to vary significantly with specific SEI species and desolvation stages. The Li⁺ vacancies in SEI species enhance complete desolvation and subsequent charge transport. Charge density and density of states calculations further demonstrate that electrolyte redox stability is closely related to SEI components. These findings provide fundamental guidance for designing SEI chemistry to enhance Li⁺ desolvation, charge transport, and electrolyte redox stability. The combined AIMD and metadynamics framework accurately models complex interfacial dynamics and energetics, yielding reliable conclusions. It can be generalized to other critical interfacial studies, such as ion transport and surface/interface stability, for applications in metal anodes, electrocatalysis, electrodeposition, and corrosion prevention.