UC Berkeley

Solid-state batteries (SSBs) are considered promising next-generation energy storage devices but tend to suffer from rapid capacity fade. Here, we demonstrate that mechanical contact loss between the solid conductor and cathode, induced by its volume changes during cycling, plays a significant role in the observed capacity fade. Focused ion beam-scanning electron microscope (FIB-SEM) tomography with nanoscale resolution was used for 3D characterization of the composite electrode morphology before and after cycling. The tomography data demonstrates the development of voids and cracks near the cathode particles and significant contact loss between the cathode particles and solid electrolyte after cycling. The observed mechanical degradation in the electrode composite highlights the difficulty and importance of engineering mechanically stable SSBs. The application of large external pressure after long-term cycling led to recovery of lost capacity and reduced the cell resistance, confirming the effect of mechanical degradation. This journal is