Optimization Approach of a PCM-Based Thermal Regulation for Lithium-Ion Batteries under High Discharge Rate and Ambient Temperatures: A Numerical Study

The performance and safety of lithium-ion batteries are highly influenced by the heat generated during operation. Excessive temperature rise can lead to thermal runaway, threatening the battery’s structural integrity and service life. Therefore, an efficient thermal management system is vital to maintain safe and stable operation, especially under high discharge rates and elevated ambient temperatures. This computational study investigates a passive-based cooling approach that combines phase-change materials with metallic structural elements to improve heat dissipation and temperature uniformity. Three composite phase-change materials (CPCMs) were formulated: CPCM1 (paraffin, expanded graphite, high-density polyethylene, and epoxy resin); CPCM2 (octadecanoic acid, octadecanol, and expanded graphite); and CPCM3 (hydrated salt and modified expanded graphite). These materials were evaluated individually and in dual-layer configurations (CPCM1-3 and CPCM2-3) to exploit their complementary melting temperatures and heat storage capacities. The thermal danger threshold was defined at 333.15 K, beyond which cell degradation or safety risks may occur. The results showed that at an ambient temperature of 293.15 K, passive-based cooling maintained all battery cells below this critical temperature, though with limited temperature uniformity. As the ambient temperature increased to 303.15 and 313.15 K, the dual-layer configurations of the phase-change material (PCM) and metallic structure system demonstrated superior performance. Specifically, at 303.15 K, the CPCM1-3 configuration reduced the maximum cell temperature by 1.92%–3.22% and the temperature gradient by up to 86.38%, remaining well below the safety threshold. At 313.15 K, the CPCM2-3 configuration maintained temperatures within 1.2% of the thermal limit and achieved a low temperature difference of 2.87 K, thereby preserving strong thermal uniformity. These findings confirm that the use of layered composite PCMs with metallic structures provides an effective passive-based thermal regulation strategy, ensuring operational safety, enhancing heat distribution, and improving the overall thermal resilience of lithium-ion battery systems.