Thermal performance optimization for cylindrical lithium-ion cells using fin-assisted multi-phase change materials

This study presents a novel multi-PCM-assisted battery thermal management system (BTMS) designed to ensure safe and efficient operation of lithium-ion batteries under high discharge rates and varying atmospheric conditions. The proposed methodology uniquely integrates four phase change materials with different melting temperatures (RT-28, RT-31, RT-33, and RT-35) within a single battery system, enabling adaptive and sequential heat absorption to maintain cell temperatures within safe limits and mitigate thermal runaway risks. Thermal performance was evaluated at 3C, 4C, and 5C discharge rates, where, in the absence of thermal management, maximum temperatures reached 66.16 °C, 74.8 °C, and 82.40 °C, respectively. The implementation of the multi-PCM BTMS reduced peak temperatures to 29.69 °C, 30.74 °C, and 31.78 °C, corresponding to reductions of 55.12%, 58.91%, and 61.43%, respectively. Among the evaluated PCMs, RT-28 exhibited superior performance, achieving the lowest temperature rise, the highest energy absorption of 1.9 kJ at 5C, and a liquid fraction of 51.17%, compared to 1.7 kJ and 44.48% for RT-31. Thermal resistance analysis further revealed stable behavior across operating conditions, with RT-35 maintaining a resistance of approximately 3.80 mΩ. Overall, the findings demonstrate that the strategic integration of multiple PCMs with staggered phase-change temperatures significantly enhances the thermal stability, safety, and reliability of lithium-ion batteries, offering a promising thermal management solution for high-power applications such as electric vehicles and renewable energy storage systems. • Thermal behavior of Li-ion batteries under high discharge rates with multi PCMs based fin assisted is studied. • Among RT-28, RT-31, RT-33, and RT-35 PCMs, RT-28 exhibiting the least temperature rise and highest energy absorption. • RT-28 maintained a liquid fraction 51.17% at 5C-rare, compared to liquid fraction of RT-31 PCM of 44.48%. • Thermal resistance increased over time for RT-28, RT-31, and RT-33, with RT-31 peaking at 3.95 mΩ. • The potential of PCM and fin assisted thermal management improve overall battery reliability.