Thermal Management of Lithium-Ion Batteries under Cyclic Charge and Discharge: Evaluation of Phase Change Materials and Air Cooling

This study systematically investigated the thermal behavior of lithium-ion batteries under different cooling strategies, including natural air convection, forced air convection, and phase change material (PCM) cooling, to mitigate thermal accumulation during operation. The experiments were performed under various discharge rates (1C, 2C, and 3C) and ambient temperatures (25, 30, and 35 °C). The results demonstrated that, under natural convection conditions, the battery temperature increased significantly with increasing discharge rate and ambient temperature. Under an ambient temperature of 35 °C and a discharge rate of 3C, the maximum surface temperature reached 86.45 °C, accompanied by a maximum temperature rise rate of 20.6 °C·min−1. At airflow velocities of 1 and 3 m s−1, the maximum surface temperatures of the lithium-ion batteries were reduced to 59.4 and 58.3 °C, respectively, corresponding to reductions of 31.29% and 32.61% compared with natural convection cooling. Under the forced convection condition with an airflow velocity of 3 m s−1, the maximum temperature rise rate was effectively suppressed below 6 °C·min−1. Among the investigated cooling strategies, PCM cooling exhibited the most stable thermal regulation capability and the highest temperature control effectiveness during repeated charge-discharge cycles. The maximum battery temperature was maintained below 50 °C, with a surface temperature difference of less than 3 °C and a temperature rise rate below 3 °C·min−1. This study provides further insights into the long-term thermal management performance of lithium-ion batteries through multi-cycle experimental evaluation and comparative analysis under various discharge rates and ambient temperature conditions. This study systematically investigates the thermal performance of lithium-ion batteries under different cooling strategies, including natural convection, forced convection at airflow velocities of 1 and 3 m s−1, and low-melting-point paraffin-based PCM cooling. Key thermal performance indicators, including the peak temperature, temperature rise rate, maximum temperature difference, and duration above 50 °C (t50), were quantitatively evaluated. The results provide valuable experimental insights into the design and selection of battery thermal management systems (BTMS) for high-rate operating conditions.