Modelling of cracks developed in lithium-ion cells under mechanical loading

This research reports on an experimental and numerical study of material failure in the electrode assemblies (i.e. “jelly roll” and/or “electrode stack”) of lithium-ion batteries after local mechanical loading. Deformed cylindrical and pouch cells (i.e. lithium-ion polymer cells) were subjected to X-ray computed tomography (CT scanning) to detect location, size, and orientation of cracks that developed in the electrode assemblies at onset of short-circuit. An experimental program was completed to acquire properties of electrode–separator micro components of electrode assemblies in tension. This data was used for calibration of an anisotropic material model. Finite element models were developed for both cell types and a maximum strain criteria was used for element failure and deletion at short circuit. The models developed here predict the location of cracks in both pouch and cylindrical cells. The finite element models corroborated the CT scan regarding location and orientation of cracks formed in the electrode assemblies. In both pouch and cylindrical cells, cracks were found to initiate perpendicular to the transverse direction of the separator.