Energy material analysis via in-situ/operando scanning transmission x-ray microscopy: A review

The development of advanced energy systems is essential for replacing fossil fuel-based societies, and progress in the fundamental understanding of solid-state energy materials has revolutionized this field. In particular, investigating the inhomogeneity of reactions in energy systems requires analysis at the level of individual particles, which are the smallest units in the system. Synchrotron-based scanning transmission X-ray microscopy (STXM) is a valuable tool for exploring reaction and degradation mechanisms, and providing nanoscale site-specific information on chemical and structural changes within single particles. In-situ/operando STXM is particularly useful for observing reactions under well-controlled conditions in real time, thus providing insights into local phenomena obscured by the ensemble effect. This review highlights the research achievements of in-situ/operando STXM in the field of energy materials and provides perspectives for advanced X-ray imaging techniques that can further enhance STXM capabilities. •STXM enables real-time imaging of chemical composition and morphological changes in nanoscale energy materials.•Operando STXM is a powerful tool to identify kinetic descriptors in complex reaction pathways of energy materials.•Operando STXM provides local information of material-surroundings interplay, aiding the reaction mechanism understanding.•Advanced STXM techniques, such as pytchography and STXM-TEY, have the potential to be implemented in operando analysis.