Impact of degradation mechanisms at the cathode/electrolyte interface of garnet-based all-solid-state batteries

All-solid-state batteries have the potential to improve the safety, energy-, and power density of lithium-ion batteries. However, the limited stability of rigid solid-solid interfaces remains a key challenge. The cathode/electrolyte interface is particularly prone to degradation during high-temperature sintering and electrochemical cycling, forming secondary phases that impede charge transport and limit cell performance. Experimental analysis of these phases is challenging since they result in thin resistive films that are sensitive to typical characterization techniques. In this study, we use structure-resolved electrochemical simulations to investigate the impact of resistive phases at the cathode/electrolyte interface on cell performance and identify dominant degradation mechanisms. We extend our simulation framework with a novel resistive film model that accounts for the additional charge transfer resistance at the interface based on interphase properties. Our approach combines continuum simulations with insights from density functional theory and experimental data, including secondary ion mass spectrometry measurements. This allows us, for the first time, to assess the impact of resistive films on the degradation of full-cell performance.