A high-order multidomain meshless algorithm for thermal management of batteries with phase change materials

To meet rising global energy demands, Lithium-ion rechargeable batteries have become a feasible solution for storing and providing energy with significantly reduced environmental degradation compared to conventional techniques. To achieve optimal performance and extended cycle life of the battery pack, it is essential to restrict the maximum temperature of Li-ion cells far below the safe operating threshold, especially at higher discharge rates. Due to their extensive application in electric vehicles and electronics, thermal management of Li-ion batteries has garnered global attention. Thus in the present study, we numerically investigate the rise in temperature of a battery pack consisting of 25 Li-ion cells subjected to hybrid cooling (air and PCM combined) at the end of discharge cycle. The battery pack is subjected to the coolant (air) flowing over the Li-ion cells at u_in=0.086, 0.172 and 0.258 m/s with each cell encapsulated with a PCM layer of thickness varying from 0-4 mm at discharge rates of 1C-5C. For the discretization of the governing equations, we have employed a high-order polyharmonic spline radial basis function (PHS-RBF) based multidomain meshless algorithm. We provide a comprehensive analysis of the increase in the average and maximum temperature of the battery pack, as well as the distribution of temperature in individual cells. Additionally, we examine the variation in the melting pattern of the PCM layer encasing the cells across different regions of the battery pack. It is seen that for higher discharge rates (i.e. discharge rate ≥ 3C), active cooling method (air cooling) is insufficient to limit the working temperature of the battery pack to the safe operating limit. The minimum effective PCM thickness required is determined to be 2 mm for a 3C discharge rate and 3 mm for a 4C discharge rate for the flow rates under consideration. At 4C discharge rate, the maximum temperature in the pack decreases by 48.7 K on increasing the PCM thickness from 0 to 4 mm. We also showcase the rise in temperature of each individual cell at the end of discharge cycle. Our observations highlight the significance of hybrid cooling techniques in alleviating the temperature of battery pack at higher discharge rates with particular emphasis on the minimum effective PCM thickness for a given C rate. This research work can be a great tool to help optimize the design of the battery pack.