Iron as a Sulfidation‐Resistant Current Collector for Negative Electrode in Sulfide‐Based All‐Solid‐Batteries

Abstract The demand for all‐solid‐state batteries (ASSBs) featuring credible Li 6 PS 5 Cl argyrodite (LPSCl) electrolytes is increasing, driving interest in exploring suitable current collectors for ASSBs. Copper (Cu), used as a current collector in traditional lithium‐ion batteries, exhibits significant instability in LPSCl‐ASSBs. In this study, the effectiveness of iron (Fe) is systematically investigated as an alternative current collector in LPSCl‐ASSBs and compare its performance to that of Cu. Electrochemical analyses reveal that Cu undergoes unfavorable side reactions with LPSCl, forming copper sulfides and leading to pitting corrosion. In contrast, Fe, with its thick native oxide layer, effectively mitigates sulfide sub‐reactions, enhancing the stability of the current collector‐LPSCl electrolyte interface. Density function theory calculations and thermal tools using XRD and linear thermammetry confirm the higher stability of Fe with LPSCl compared to Cu. Replacing the Cu current collector with Fe significantly improves the long‐term stability of graphite‐based negative electrodes in ASSBs, achieving exceptional long cycleability exceeding 1000 cycles. These findings identify Fe as a promising current collector for ASSBs and provide valuable insights into the metal‐electrolyte interactions that govern the performance of these advanced battery systems.