Reveal the Origins of Reaction Heterogeneity in Battery Electrodes by Combining X-Ray Imaging and Mesoscale Modeling

Non-uniform redox reactions in battery electrodes play an important role in causing inferior battery performance and stability. Synchrotron X-ray imaging techniques provide a powerful suite of tools for characterizing the reaction distribution and evolution in batteries across multiple length scales. In this talk, we will present several examples where they are combined with mesoscale modeling to contribute to a mechanistic understanding of the reaction heterogeneity phenomena. At the particle agglomerate level, we applied 3D XANES imaging to determine the phase transition pathway in LiFePO₄ secondary particles. It was discovered that the transformation strain gives rise to a filamentary domain morphology, which persists even at very high (dis)charge rates. At the cell level, we measured the state of charge (SOC) distribution in thick porous electrodes by conducting 2D XANES mapping in the fluorescence mode. A comparative study of LiFePO₄ vs NMC622 reveal that the reaction gradient across the electrodes is controlled by not only the charge transport kinetics but also the intrinsic properties of the active materials. Moving beyond lithium-ion, we studied the morphological instability of zinc metal anode in aqueous electrolyte via operando nanotomography. Our observations elucidate the growth and dissolution mechanisms of zinc mossy structure and shed light on an effective approach to achieve uniform zinc deposition.