Toward Ultrastable Metal Anode/Li₆PS₅Cl Interface via an Interlayer as Li Reservoir

All-solid-state sulfide-based Li metal batteries are promising candidates for energy storage systems. However, thorny issues associated with undesired reactions and contact failure at the anode interface hinder their commercialization. Herein, an indium foil was endowed with a formed interlayer whose surface film is enriched with LiF and LiIn phases via a feasible prelithiation route. The lithiated alloy of the interlayer can regulate Li⁺ flux and charge distribution as a Li reservoir, benefiting uniform Li deposition. Meanwhile, it can suppress the reductive decomposition of the Li₆PS₅Cl electrolyte and maintain sufficient solid-solid contact. In situ impedance spectra reveal that constant interface impedance and fast charge transfer are realized by the interlayer. Further, long-term Li stripping/plating over 2000 h at 2.55 mA cm^-2 is demonstrated by this anode. All-solid-state cells employing a LiCoO₂ cathode and the Pre In anode can work for over 700 cycles with a capacity retention of 96.15% at 0.5 C.