Linking void and interphase evolution to electrochemistry in solid-state batteries using operando X-ray tomography

Despite progress in solid-state battery engineering, our understanding of the chemo-mechanical phenomena that govern electrochemical behaviour and stability at solid-solid interfaces remains limited compared to at solid-liquid interfaces. Here, we use operando synchrotron X-ray computed microtomography to investigate the evolution of lithium/solid-state electrolyte interfaces during battery cycling, revealing how the complex interplay among void formation, interphase growth and volumetric changes determines cell behaviour. Void formation during lithium stripping is directly visualized in symmetric cells, and the loss of contact that drives current constriction at the interface between lithium and the solid-state electrolyte (Li10SnP2S12) is quantified and found to be the primary cause of cell failure. The interphase is found to be redox-active upon charge, and global volume changes occur owing to partial molar volume mismatches at either electrode. These results provide insight into how chemo-mechanical phenomena can affect cell performance, thus facilitating the development of solid-state batteries.

Automated summary

The study using operando synchrotron X-ray computed microtomography reveals the evolution of lithium/solid-state electrolyte interfaces during battery cycling, showing how void formation, interphase growth, and volumetric changes affect cell behavior. Loss of contact at the interface between lithium and the solid-state electrolyte is found to be the primary cause of cell failure, while redox-active interphase and global volume changes upon charge also play significant roles in determining cell performance. These findings provide insights into the impact of chemo-mechanical phenomena on cell behavior, aiding in the development of solid-state batteries.