Transport and Failure in Li-ion Batteries

While battery performance is well predicted by the macrohomogeneous model of Newman and co-workers, predicting degradation and failure remains a challenge. It may be that, like most materials, failure depends on local imperfections and inhomogeneities. We use tomographic data to evaluate the homogeneity of the tortuosity of the electrode by directly integrating the transport equations through its pore space. The tortuosity of two halves of the local tortuosity variations up to a factor of 4 are observed. The relationship between porosity and tortuosity is not well predicted by the Bruggeman relationship for this electrode, either locally or globally. We suggest that large local variations in tortuosity can lead to reduced capacity and life because of concomitant changes in current density.