Extension of the Newman-P2D-Model for Cracks and Open Pores – Modelling States of Degradation

Cycle aging of Li-ion batteries can result in a variety of interconnected degradation processes. High-nickel cathodes show both changes to their surface chemistry, as well as to the particle morphology. As a result, distinguishing between the effects of individual degradation mechanisms is highly challenging without the use of extensive post-mortem analysis. To overcome this limitation, a physics-based battery model based on the established Doyle-Fuller-Newman-Model is proposed, which allows for deeper insight into a given morphological state of degradation. This is done by modelling the presence of cracks and pores in the secondary particles. Cracked particles are simplified to representative fragments, surrounded by electrolyte films of varying size. Building upon the electrode scale transport considered by Newman, mass and charge transport in fragments and electrolyte filled cracks, as well as the reaction at the crack interfaces is modelled. The fundamental capabilities of the model are shown in a parameter variation study, based on literature parameters. The impact of the inner geometry and conductivity of the active material on the utilization of the crack interface, and therefore the charging behavior of the battery, is shown.