Multi-scale Imaging of Solid-State Battery Interfaces: From Atomic Scale to Macroscopic Scale

Summary. Solid-solid interfaces play a crucial role in fundamental aspects of electron transfer and ion transport, which determine the underlying physical phenomena and electrochemical behaviors in solid-state batteries. Nevertheless, the exact mechanisms at the solid-state battery interface have not been fully elucidated, which necessitates the localized probes to comprehensively understand their physical contact, interphase formation, interfacial instability, and mechanical properties. In this review, a variety of emerging imaging techniques to understand the local structure and chemistry at solid-state battery interfaces are overviewed, with special focus on how each imaging technique can address the key challenges at cathode-electrolyte interfaces, anode-electrolyte interfaces, and interparticle interfaces from the atomic scale to the macroscopic scale. The capabilities and limitations of these imaging methods are summarized and discussed. We also provide a vision of the state-of-the-art imaging characterization techniques and highlight new operando capabilities from cryogenic or synchrotron imaging methods to track the dynamic solid-state interface behaviors.