Modeling of dynamic mechanical response of Li-ion cells with homogenized electrolyte-solid interactions

Several recent studies have revealed substantial strain-rate dependence of lithium-ion batteries subjected to dynamic mechanical loadings. This behavior has been shown to be strongly dependent on the cell type, geometry, and setting. While still far from being fully understood, this dependence is believed to be connected to the solid-liquid interactions between the porous solid materials inside the electrodes and separators and the liquid electrolyte. This understanding has been supported by tests on dry cells revealing a significantly simpler behavior, being determined primarily by the constitutive material properties as compared to wet cells. This paper provides a modeling approach for the fluid-solid interaction inside battery cells by utilizing a pore fluid movement feature originally developed for geo-materials. By applying this module to the dry cell structure, the essentials of the peculiar load displacement patterns observed with active cells could be reproduced for two types of cells, a prismatic and a pouch cell. It is believed that this procedure, elucidating the underlying physics, and yet being simple, effective, and less time consuming than potential alternative techniques, will be exceedingly useful for evaluating crash behavior of electric vehicles. It allows making realistic calculations feasible based on experiments performed only on dry cells quasi-statically.