(Invited) Multiscale Analysis of Battery Materials Using X-Ray Microscopy

Abstract

Battery electrodes are inherently multiscale, functional material systems that provide sites for chemical reactions and pathways for charge and reactant transport. A greater understanding of the interaction between transport phenomena, electrochemistry, and electrode structures is critical to advance battery performance and reliability. Direct microstructural imaging methods provide a unique capability for the multiscale observation of electrode structures and the material changes that occur during battery operation. The microstructural image data produced by these methods also facilitates physics-based simulation informed by real device structures. Applications of X-ray microscopy to battery electrodes at multiple scales are presented. X-ray nanotomography (XNT) and microtomography (µCT) of battery electrode materials are presented for high capacity metallic anode materials and transition metal oxide cathode materials. First, X-ray imaging is presented as a means of assessing the impact of processing methods on electrode structure at nano- and micro-scales. Ex situ and in operando spectroscopic imaging using µCT and nano-scale X-ray absorption near edge structure (XANES) are then presented as a means of assessing multiscale chemical and structural changes in electrodes during cycling. The data obtained through these imaging efforts facilitates modeling of real electrode structures. Modeling efforts informed by the microstructural data obtained are discussed with a focus on Li-ion cathode materials. Observations from modeling are complemented by microstructural analysis that permits description of cathode performance in terms of dimensionless parameters.