Unraveling Lithium-Ion Transport in Solid Electrolyte Interphase: from Composition to Interface Dynamics via Molecular Dynamics Simulations.

Lithium-ion transport across the solid electrolyte interphase (SEI) is a key procedure in charging which determines the performance and stability of lithium-ion batteries (LIBs). However, an atomic-level understanding of the overall transport process from electrolyte through SEI remains elusive, particularly regarding the thermodynamic and kinetic parameters that govern this cross-interface phenomenon. In this study, molecular dynamics (MD) simulations are employed to systematically investigate the complete Li-ion transport progress, encompassing the electrolyte, organic/inorganic SEI components, and two critical interfaces: electrolyte/organic SEI and organic SEI/inorganic SEI. The results indicate that Li ions in the organic SEI retain either full or partial solvation shells. Free energy profiles reveal that the highest energy barrier emerges at the organic-inorganic SEI interface due to the complete desolvation of Li ions and structural differences between the organic and inorganic SEI layers. By constructing a comprehensive free energy landscape for Li-ion transport, this study offers valuable insights into the relationship between SEI composition, structure, and interfacial dynamics.