July 2020 - The broad use of global or spatially averaging measurements over a battery cell to characterize highly localized Li-plating phenomenon in Lithium-ion batteries during fast-charging has created a disconnect between measurements and the underlying causes. Consequently, the field is missing a clear path to implementing fast-charging, as well as expanding the envelope into extreme fast-charging (XFC, defined here as =6C in =10 min). Aiming to bridge these gaps, this study presents a detailed look into the local detection of Li-plating and the consequent cycle-life implications for electrodes and cells under XFC conditions by utilizing electrochemistry and high-energy X-ray diffraction. Significant heterogeneity in Li metal plating during XFC results in accelerated and non-uniform cycle-life losses, in contrast to prevailing acceptance that C-rate is correlated to Li plating for XFC. This behavior is triggered by local electrode heterogeneity, which has yet to be identified and is not apparent in volume-averaged quantifications. This work suggests that better understanding of these multiscale local-electrode heterogeneities is crucial for identifying pathways to enable XFC.