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Abstract Electronic connections between active material particles and the conductive carbon-binder-domain govern the rate capability and lifetime of high-energy commercial Li-ion batteries (LIB). This work develops an in-situ electrochemical fluorescent microscopy (EFM) technique that maps fluorescence intensity to these local electronic connections. Specifically, rapid redox kinetics of an electrofluorophore translates to reaction distributions that are limited by electronic accessibility of battery electrode regions and individual active material particles. This technique can visualize hot-spots, dead zones, and isolated particles on the electrode surface. EFM characterization of a series of LiNi0.33Mn0.33Co0.33O2 electrodes across processing parameters finds a significant negative correlation between the number of disconnected active particles and the rate capability. This low-cost technique provides quantitative mesoscale characterization of commercial LIB electrodes with fast throughput (<60 s) to facilitate rapid research and development and provide manufacturing quality control.
Negrete et al. (Mon,) studied this question.