Heterogeneous Particle Dynamics Driving Macroscopic Degradation in Porous Electrodes

A Fokker-Planck model that describes the resistance evolution of a population of battery particles is formulated from the idea of a fitness landscape, borrowed from ideas in population genetics. This model incorporates of particle size and heterogeneous degradation accumulates in the particles as the battery is cycled, where resistance formation, surface blockage, and loss of lithium capacity mechanisms are accounted for. A non-homogeneous amount of resistance buildup is formed on the particles which is dependent on the size of the particles, which eventually builds up to rollover failure. Contributions from the heterogeneous degradation, especially at the smaller particles, are observed to contribute to the nonlinear behavior of degradation. It is observed that different degradation mechanisms result in different shapes of the capacity loss curve in the electrode. Macroscopic voltage curves and capacity loss information can give insight into the dominance of different degradation mechanisms.