Optimizing battery thermal management with phase change materials: Influence of thickness, ambient conditions, and material selection

Effective thermal management is critical for maintaining the performance, safety, and lifespan of lithium-ion batteries, which operate most efficiently within a narrow temperature range of 20–40 °C. Exceeding this range can lead to accelerated degradation, uneven aging, and capacity loss. We numerically investigate the thermal performance of a passive battery thermal management system employing phase change materials (PCMs) for temperature regulation in cylindrical lithium-ion cells. The effects of PCM thickness (1–7 mm), ambient temperature (20–50 °C), PCM type, external convective heat transfer coefficient, and PCM fill volume (33 %, 66 %, and 100 %) are systematically examined under discharge rates ranging from 2C to 5C. The model is validated against experimental measurements of battery surface temperature under various discharge conditions, showing a mean deviation under 5 %. Simulation results show that a PCM with a melting point near 35 °C offers the best balance between temperature control, latent heat utilization, and thermal uniformity under moderate ambient conditions. While thicker PCM layers reduce peak battery temperatures, they also increase thermal resistance, leading to greater temperature gradients and underutilization of the outer PCM region. Among the tested materials, lower-melting-point PCMs are more effective at low ambient temperatures, whereas higher-melting-point PCMs perform better under elevated thermal loads. Increasing the external convective heat transfer coefficient from 5 to 20 W/m 2 K enhances surface cooling and steepens the thermal gradient, improving temperature regulation. However, it also accelerates energy dissipation to the environment, reducing PCM melt fraction and latent heat utilization. Finally, higher PCM fill volume delays thermal saturation and extends the effective cooling period, resulting in improved thermal regulation across the discharge cycle. • PCM reduces peak temperature by up to 42 % at 4C discharge, enhancing thermal stability. • A 4 mm PCM layer balances thermal performance and material usage • A validated numerical model achieves <5 % deviation from experimental battery data. • A higher heat transfer coefficient improves PCM effectiveness but increases thermal gradient. • RT-35 excels in moderate conditions, while RT-24 and RT-47 suits for harsh environments.