Local microstructure-induced fluctuations in Li-Ion battery: theory and simulations

Abstract

In recent years, a microstructure-resolving theoretical framework based on non-equilibrium thermodynamics was developed that allows describing electrochemical processes in electrodes of Lithium-ion batteries. A comparison of its predictions with those of the classical porous electrode theory by Newman and coworkers reveals that the models generally agree about averaged characteristics (charge curve, etc.), albeit with small noticeable systematic shifts. At the same time, localized fluctuations in potential and ion concentration, sometimes on the order of their averaged values, show up in the microstructure theory but are absent from the Newman theory predictions. The presence of these fluctuations can modify qualitatively the porous electrode theory-based predictions about local degradation and dissipation processes (Li plating, SEI growth, heat generation). Using a combination of formal homogenization and perturbation frameworks, we show how these fluctuations can be included in a porous electrode description and analyze which factors influence the scale of fluctuations (OCV curve, particle shape, etc.). The theoretical findings are supported by numerical simulations. In the light of big computational costs of the microstructure-resolving simulations, we proposed a new Li-Ion cell model that combine accurate prediction of the localized fluctuations with the numerical efficiency of the classical Newman’s model.