Quantifying electronic insulation of solid-electrolyte interphases through electrolyte decomposition kinetics

The pursuit of high operating voltage and energy density of battery packs imposes stringent requirements on the electronic insulation of solid-electrolyte interphases (SEI) in rechargeable lithium-ion batteries. Owing to complicated kinetic processes, direct experimental characterization of electronic insulation poses challenges, whereas first-principles computations provide valuable access to underlying microscopic parameters. However, existing methods often yield conflicting evaluations by focusing solely on electronic transmission at specific parts of SEI/electrolyte interfaces, ignoring electrolyte decomposition kinetics. Herein, we develop a computational framework combining the Marcus electron transfer model and constrained density functional theory to predict the resistance to electrolyte decomposition ( R ED ), which quantifies how effectively the SEI suppresses decomposition. R ED unifies two key physical factors: electronic transmission across interfaces and reorganization energy associated with electrolyte decomposition, thereby enabling component‑resolved, electrolyte‑dependent evaluation of SEI electronic insulation. Applying the framework to idealized crystalline graphitic C(0001)|SEI | electrolyte interfaces, we find that electrolyte-dependent reorganization can substantially alter, and in some cases reverse, the insulation ranking inferred from electronic coupling alone, identifying reorganization as a key contributor to the comparatively high electronic insulation of Li 2 CO 3 in the systems examined. The present work establishes a proof-of-concept, component-resolved framework and a basis for future studies of structurally heterogeneous SEIs.