Visualization of Electrochemical Reactions in Battery Materials with X-ray Microscopy and Mapping

Unlocking the full performance capabilities of battery materials will require a thorough understanding of the underlying electrochemical mechanisms at a variety of length scales. A broad arsenal of X-ray microscopy and mapping techniques is now available to probe these processes down to the nanoscale. The tunable nature of X-ray sources allows for the extraction of chemical states through spectromicroscopy. The addition of phase contrast imaging can retrieve the complex-valued refraction of the material, giving an even more nuanced chemical picture. Tomography and coherent Bragg diffraction imaging provide a reconstructed three-dimensional volume of the specimen, as well as internal strain information from the latter. Many recent insights into battery materials have been achieved through the creative use of these, and similar, methods. Experiments performed while the battery is being actively cycled reveal behavior that differs significantly from what is observed at equilibrium and metastable conditions. Planned improvements to X-ray source brightness and coherence will extend these techniques by alleviating the current trade-off in time, chemical, and spatial resolution.