Calendering-induced interfacial reconfiguration enables electrochemical activation in lithium metal powder electrodes for high-energy-density batteries

Abstract

To address the difficulty in achieving both thin and wide lithium (Li) metal electrodes using conventional extrusion and pressing methods, a slurry-based coating process with lithium metal powder (LMP) is considered a promising alternative. By adjusting the coating conditions, this technique allows the fabrication of ultra-thin and wide Li metal electrodes. However, the Li₂CO₃ passivation layer formed to enhance storage stability is electrically insulating and must be mechanically disrupted prior to using the LMP electrode as an anode. The calendering process, conducted after LMP slurry coating and drying, serves as an essential step that fractures the brittle Li₂CO₃ layer and exposes the underlying fresh Li metal within the LMP particles. The exposed ductile Li directly contacts adjacent particles or the Cu current collector, thereby extending the electrically conductive network within the electrode and contributing to the formation of electrochemically active LMP. In this study, we systematically investigate how the calendering process affects the structural evolution and electrochemical activation of LMP electrodes. Under varying calendering ratios (from 0% to 40% and 40%+), we examined the correlation between electrode structural changes, Li₂CO₃ fracture, electrical connection, and the degree of electrochemical activation. Electrochemical activation increased nonlinearly with the calendering ratio, with a critical threshold near 35%. The optimal calendering conditions for LMP activation were determined through experimental validation and simulation analysis.