Origin of Solid Electrolyte Interphase Heterogeneity on Lithium Metal Anodes and Its Mitigation with Electrolyte Additives

Abstract

Lithium metal anode (LMA) stands as a promising candidate for next-generation high-energy-density batteries, yet its viability is critically compromised by heterogeneous solid electrolyte interphase (SEI) formation. This interfacial inhomogeneity manifested as spatially fluctuating Li⁺ transport kinetics provokes erratic lithium deposition and dendrite propagation. Here, we reveal that current strategies to homogenize SEI are impeded by an overlooked origin: crystallographic anisotropy-driven adsorption bias of electrolyte components across polycrystalline Li (poly-Li) surfaces, thereby dictating SEI heterogeneity. We further decouple the correlation between lattice orientation and adsorption energetics by engineering a dual-additive electrolyte [fluoroethylene carbonate (FEC) and propane sultone (PS)]. These additives establish plane adsorption uniformity, forming a homogeneous SEI that spatially synchronizes Li⁺ flux. When paired with a high-loading LiCoO₂ cathode (3.86 mAh cm^–2), the stabilized anode enables 80% capacity retention over 380 cycles under ultralean conditions (N/P = 2.30, E/C = 2.34 g Ah^–1), tripling the cycle life versus conventional electrolytes while suppressing dendritic failure modes.