Thermal design optimization of laminated lithium ion battery based on the analytical solution of planar temperature distribution

Thermal issues constitute a major barrier to the deployment of large-format lithium ion batteries on electrical vehicles. Thermal modeling is a powerful tool to investigate the thermal design and improve the thermal performance of the battery. There are two methods to solve thermal models, the numerical simulation and the analytical solution. Most of the thermal modeling works reported in the literature are based on the numerical simulation. However, the analytical solution is highly desirable for optimization as it allows the effects of mutiple thermal parameters to be evaluated simultaneouly, thanks to its low computational cost. This work firstly proposes and validates a numerical thermal model for a 25 Ah laminated lithium ion battery. The simulated temperatures agree well with the experiment results from multiple thermocouples. Secondly, an analytical solution to the planar temperature distribution is deduced using the integral transform technique, assuming that the temperature distribution is two-dimensional and the heat generation rate is uniform. These assmuptions are justified from the simulation results. Finally, the analytical solution is used to optimize the battery thermal design, including the optimal core aspect ratio and the tab displacement.