Advancing Energy Materials by Multimodal <i>Operando</i> Electrochemical Transmission Electron Microscopy

Energy materials are central to the global transition toward a sustainable, carbon-neutral energy landscape. However, their structural transformation under operating conditions poses a significant challenge in understanding reaction mechanisms. Here, we present recent advances in operando electrochemical liquid-cell scanning transmission electron microscopy (EC-STEM) to probe time-resolved nanoscale dynamics of energy materials at solid-liquid interfaces. We highlight quantitative electrochemistry through reliable calibration of applied potentials with beam-dose control. Operando EC-STEM introduces controlled environmental stimuli to simulate realistic operating conditions and offers a multimodal characterization platform by incorporating complementary operando X-ray and vibrational spectroscopy and cryogenic TEM methods across multiple spatiotemporal scales. Furthermore, integration with machine learning/artificial intelligence (ML/AI) algorithms effectively addresses critical challenges of EC-STEM, including low signal-to-noise ratio and massive volumes of time-series datasets. We emphasize the need to calibrate and benchmark energy materials' performances in confined liquid environments with minimal beam-induced damage. This perspective will catalyze widespread adoption of advanced operando TEM across general energy materials and electrochemistry communities.