Operando X-Ray Diffraction Nanoimaging of Advanced Cathodes

Abstract

Techniques capable of probing active materials in situ are increasingly needed to link cell performance data with nanostructural evolution inside functional devices. Rapid improvements in spatial and temporal resolution of X-ray nanomicroscopy and high-energy diffraction facilitated by new 4th-gen synchrotrons offer a powerful platform for investigating phase transitions inside advanced cathode materials. We show how the latest methodologies can be used to evaluate the mechanism of phase transitions at the nanoscale, linked to degradation processes inside commercially relevant cells."Single crystal" cathode active materials have garnered incredible academic and industrial interest in the past several years. Despite extensive electrochemical performance validation, there remain very few tools capable of evaluating the quality and consistency of these materials. Scanning X-ray nanodiffraction microscopy reveals the hidden microstructure and defects inside nominally single crystal cathode particles established during their fabrication. In situ nanodiffraction imaging provides further insight towards the link between this microstructure and functional properties such as high voltage stability inside individual crystallites during cycling.