Li-ion Battery Cooling - A Computational Study of Different Phase Change Material Configurations

Abstract

Overheating of Li-ion batteries in Electric Vehicles (EVs) degrades performance and reduces lifespan. Hence, energyefficient and reliable Battery Thermal Management Systems (BTMS) are required. This paper investigates the use of Phase Change Materials (PCMs), a passive cooling method with high heat storage capacity, for the thermal management of prismatic Li-ion battery cells in EVs. This computational study models the influence of buoyancy-driven convective flow on the PCM cooling performance, compared against thermal conduction-only models. In addition, this study investigates how convective flow influences the cooling performance with variations in cell orientation between vertical and horizontal alignments. n- Octadecane is used as the PCM, and Computational Fluid Dynamics (CFD) simulations were conducted with the Solidification and Melting model in ANSYS Fluent. A 12 mm PCM layer placed around the cell periphery reduced the centre temperature after 1800 s by 2.7 K in the vertical orientation and 3.7 K in the horizontal orientation compared to air-cooling. The effect of natural convection was more pronounced in the horizontal orientation, providing superior cooling performance relative to the vertical case. When the same PCM volume was used to fully enclose the cell, the cooling effect was further enhanced, achieving a maximum temperature reduction of 8.3 K within the first 1800 s. The findings demonstrate that natural convection significantly enhances the PCM-based cooling effectiveness, particularly in horizontally oriented cells, while thinner PCM layers with increased heat transfer area promote faster melting and improved cooling performance.