With the growing demand for sustainable battery technologies, state-of-the-art characterization techniques become more and more critical for optimizing battery materials and uncovering their operation mechanisms. In this Review, we mainly focus on X-ray imaging techniques and the associated applications in obtaining insights into the physicochemical properties and quantitative changes of battery materials. Given the high-energy nature of X-rays, operando/in situ imaging studies have emerged as a unique method to enable researchers to investigate a variety of battery chemistries during battery cycling. Such a cutting-edge characterization tool is expected to advance the understanding of electrochemically driven heterogeneous reactions, involving the structure, chemistry, and morphology, as well as the interface. Mechanistic explanations are comprehensively provided to understand the close relationship between battery failure and electro-chemo-mechanical degradation in the electrode. We expect that the use of large-scale X-ray facilities can lead to major developments in sustainable batteries and benefit the whole materials science community.