How Fast Do Elevated Temperatures Reach the Cell Interior?

The research team from NEXT ENERGY EWE Research Centre for Energy Technology at the University of Oldenburg set out to investigate whether the manufacturing process could cause irreversible damage to lithium-ion cells due to elevated temperatures. They used numerical simulation to model different operating scenarios and placed probes to inspect results at any point in the model. The first step was to set up a physical experiment to measure temperatures reached inside a prismatic lithium dummy cell when subjected to short-term thermal stress. The goal was to collect data to validate the mathematical model and investigate the effect of various processes during cell manufacturing. The team created a 3D replica of a commercial prismatic lithium cell in Autodesk Inventor software and imported it into the COMSOL Multiphysics software. They modeled heat transfer by conduction due to an external heat source at different positions on the cell corresponding to different manufacturing processes, and the natural convective cooling on other areas of the cell surface. The physical and thermal properties of the individual materials were experimentally defined and mathematically homogenized into one jelly roll domain within a prismatic steel housing. Adaptive mesh refinement was used to adopt a finer discretization in regions where temperature gradients were higher, ensuring high-accuracy results.