High-energy x-ray (HEX) scattering is a sensitive and powerful tool to nondestructively probe the atomic and mesoscale structures of battery materials under synthesis and operational conditions. The penetration power of HEXs enables the use of large, practical samples and realistic environments, allowing researchers to explore the inner workings of batteries in both laboratory and commercial formats. This article highlights the capability and versatility of HEX techniques, particularly from synchrotron sources, to elucidate materials synthesis processes and thermal instability mechanisms in situ, to understand (dis)charging mechanisms in operando under a variety of cycling conditions, and to spatially resolve electrode/electrolyte responses to highlight connections between inhomogeneity and performance. Such studies have increased our understanding of the fundamental mechanisms underlying battery performance. By deepening our understanding of the linkages between microstructure and overall performance, HEXs represent a powerful tool for validating existing batteries and shortening battery-development timelines.