Quantifying the Interfacial Energy Gap for Reversible Lithium-Metal Anodes

Lithium-metal batteries (LMBs) hold great promise for high-energy-density energy storage yet suffer from low Li plating/stripping Coulombic efficiency (CE), which originates from persistent electrolyte decomposition at the electrolyte/anode interface. Such parasitic reactions are driven by interfacial electron transfer, closely tied to both the passivation capability of solid electrolyte interphase (SEI) and reductive stability of electrolytes. Herein, the interfacial energy gap (ΔEgap) between Fermi level of Li/SEI and lowest unoccupied molecular orbital level of electrolyte is proposed as a descriptor to quantify the driving force for interfacial electron transfer, demonstrating that a reduced ΔEgap could effectively suppress interfacial parasitic reaction and thus enhance Li CE. Machine learning modeling coupled with Shapley additive analysis identifies the solvent minimum electrostatic potential (ESPmin) as the dominant governing factor of ΔEgap. Guided by these insights, we design two out-of-sample solvents with small ΔEgap, achieving high CEs exceeding 99%. Combined experimental and simulation results elucidate an ESPmin-governed interfacial regulation mechanism. This work provides a quantitative and interpretable strategy for rational electrolyte design toward highly reversible LMBs.