Nanoscale Projection Hard X‐ray Microscope for Operando Statistical Analysis of Chemical Heterogeneity in Lithium‐Ion Battery Cathodes

The spatiotemporal heterogeneity of the state of charge (SOC) within battery electrodes significantly impairs the rate capability and cycle life of lithium-ion batteries. However, mapping this heterogeneity is challenging owing to the lack of experimental methods that quantify the SOC at the electrode scale, while also offering nanoscale resolution for in-depth analyses of individual particles. Herein, this work reports an advanced projection X-ray microscopy that combines nanometric resolution, a large field of view, and high chemical sensitivity using spectroscopic imaging. This method enables the operando imaging of SOC heterogeneity across electrodes containing numerous Ni-rich layered oxide (NRLO) particles, while significantly lessening the radiation dose and maintaining rapid imaging speeds. This work characterizes the SOC heterogeneity in the degraded electrode with a cross-section, thereby revealing the considerable heterogeneity in the battery degradation progresses at the individual-particle-level. Further, this work observes inter- and intra-particle heterogeneity during NRLO particle calcination, thereby identifying rapidly oxidized particles that likely facilitate the calcination process.