Heterogeneous Damage and Network Evolution in Composite Electrodes of Li-Ion Batteries

We assess the heterogeneous electrochemistry and mechanics in a composite cathode using synchrotron X-ray tomography, machine learning, and microstructure-resolved computational modeling. We visualize the morphological defects at multi-scales ranging from the macroscopic composite, particle ensembles, to individual single particles. Particle fracture and interfacial debonding are identified in a large set of tomographic data. The mechanical failure of active particles is highly heterogeneous. The difference originates from the polarization of the electrolyte potential, various local conducting environments, and thus the non-uniform distribution of the activation energy for the charge transfer reaction. We model the kinetics of intergranular fracture and interfacial degradation to assess the heterogeneous mechanical damage in composite electrodes. We quantify the influence of the mechanical damage on the metrics of battery performance. The mechanical failure disrupts the conduction path of electrons and results in significant polarization and capacity loss in batteries. More interestingly, the interfacial failure may reconstruct the conductive network and redistribute the electrochemical activities that render a dynamic nature of electrochemistry and mechanics evolving over time in the composite electrodes.