This proposal aims to develop new multidimensional operando synchrotron methods for studying Li-ion batteries (LIBs). These methods are necessary to visualize and model the complex interplay between solution-phase and solid-phase concentration gradients in LIBs. The formation of these gradients is the main reason commercial LIB architectures cannot consistently undergo fast (dis)charge. Currently, no analytical method can observe both solution-phase and solid-phase concentration gradients simultaneously in LIBs. In collaboration with the ESRF, we recently demonstrated the ability to visualize both the solution-phase Li+ gradient and solid-phase state of charge (SoC) simultaneously through tandem X-ray fluorescence (XRF) and X-ray diffraction (XRD) at the ID-31 beamline. We now want to expand this work by providing full cell concentration and SoC mapping for the first time and capitalizing on ID-31 capabilities to study ultra-fast discharge limitations in composite electrodes.