<i>Operando</i> X‐Ray Diffraction and Total Scattering Characterization of Battery Materials: Not Just a Pretty Picture

ABSTRACT The development of rechargeable batteries can be accelerated by the fundamental understanding of their chemistries. Multiple characterization techniques have been deployed to study the chemical processes in batteries, but structural studies at the atomic level using X‐ray diffraction (XRD) and total X‐ray scattering (TXS) show enduring popularity. These methods are relatively easy to apply in operando mode, where structural data is collected alongside electrochemical data under operating conditions. With a growing interest in this powerful methodology, it is important to review the general principles of operando XRD/TXS characterization and develop a set of guidelines for the collection, analysis, and presentation of data that are acceptable to the community and can lead to reliable, representative, and reproducible results that are easy to judge and compare. This Review aims to survey and discuss important steps in operando XRD and TXS. From cell and electrode design to data treatment, we survey the major experimental aspects of operando studies, pointing out potential pitfalls and identifying best‐practice. In addition, we review some unconventional experiments conducted in operando mode to illustrate how such methods can be used beyond studies of the early‐stage cycling mechanisms of battery active materials.