Impacts of key physical parameters on the cycling of thin metallic lithium in sulfide-based all-solid-state batteries

Sulfide-based solid electrolytes (SE), when paired with thin metallic lithium anodes and high voltage cathodes, hold great promise for safe and high energy density all-solid-state batteries (ASSBs). However, stable cycling at high current densities and areal capacities remains hindered by dendritic lithium growth and “dead” lithium formation. In this study, we systematically investigate the influence of key physical parameters on the cycling performance of 50 μm metallic lithium using Li₆PS₅Cl as the SE in a bulk-type ASSB stack. Specifically, we assess lithium edge protection, SE fabrication, stack assembly and cycling pressures, and formation cycles at low current density. We demonstrate that in lithium symmetric cells, optimizing these parameters, along with well-designed cells ensuring tight sealing and uniform pressure distribution, allows reaching 1.9 mA cm⁻² at room temperature and extends the lifetime to over 500 cycles at 1 mA cm⁻² and 1 mAh cm⁻², without interfacial chemical modifications. Full cells employing LiNi_0.8Co_0.1Mn_0.1O₂ cathodes and 50 μm Li anodes sustain 1C (2.85 mA cm⁻²) during rate capability testing and achieve stable cycling over 100 cycles at C/3 (0.95 mA cm⁻²) with an average areal capacity of 1.4 mAh cm⁻². This work offers insights and guidelines to improve cycling reproducibility and reliability in Li metal ASSBs, advancing their path toward practical deployment.