Application of X‐ray Pair Distribution Function to Batteries

This chapter focuses on the atomic pair distribution function (PDF) method as applied to the study of energy storage materials. The PDF technique stands out as a powerful tool to detect short- and intermediate-range order in materials on the nanoscale. It may be obtained from the entire Bragg and diffuse scattering signals using X-rays, and it can encode structural details when defects, disorders, or structural ambiguities obscure their elucidation directly in reciprocal space. Significant progress has been made in its application to probe functional materials such as carbons, liquids, composites, and more. Here, we will provide an overview of the basic principles, data analysis methods, and special features of the PDF method. Moreover, its practical application in a variety of energy storage materials and systems is presented. For each application, a brief discussion of the structure-performance coupling will be given, followed by selected cases of the PDF investigations. Effective utilization of this method needs a combination of interdisciplinary consolidation of material preparation, accurate data processing, high-quality scattering experiment, model formulation, and attentive scrutiny of the results. It is hoped that this chapter will provide a meaningful reference to practitioners for PDF in a wide field of energy storage sciences and so on and help new practitioners to get started with this technique.