An Janus-type buffer layer with ion conductive and electron insulative interface enabling dendrite-free solid-state lithium metal batteries

The cycle life of garnet-based solid-state lithium-metal batteries is limited by interfacial lithium deposition behaviour. In this study, we propose an innovative buffer layer for the electrolyte-lithium anode interface that combined interfacial dynamics with lithium-metal compatibility. A heterogeneous nanofiber buffer layer of LLZO@MoS₂, possessing bifunctional ion transport and electronic insulation, has been successfully developed, effectively regulating the potential distribution at the interface to ensure uniform lithium ion deposition. Meanwhile, LLZO@MoS₂composite polymer intermediate layer heterogeneous nanofibers is employed to optimize potential distribution on the lithium metal surface. This design leverages enhanced interfacial compatibility to effectively mitigate electron leakage from Li to LLZO grain boundaries/defects, optimize Li⁺ transport kinetics, and consequently improve cycling stability at high current densities. The unique buffer layer enables a critical current density (CCD) of 1.5 mA cm⁻². The resulting symmetric cells exhibit an impressive 2000 h cycle life at a practical current density of 0.8 mA cm⁻². When paired with a variety of cathodes, it provides stable and highly reversible capacity. Specifically, the assembled NCM811 cell has a highly reversible capacity of 188 mAh g⁻¹ at 0.1 C and a good cycle stability of 1000 cycles at 0.5 C. This finding breaks with conventional strategies aimed at improving the overall performance of solid-state lithium-metal batteries with LLZO-based composite electrolytes (LLZO CSE) and significantly optimises the lithium deposition behaviour during cycling.