Analysis of Influencing Factors in the Thermal Management System of Cylindrical Lithium-Ion Batteries Based on CPCM under High Discharge Rates

With the rapid development of new energy vehicles, lithium-ion batteries (LIBs) have been widely used in the automotive sector. The performance and safety of LIBs in electric vehicles (EVs) are significantly influenced by operating temperature, making the development of an effective battery thermal management system (BTMS) crucial. In recent years, phase change material (PCM)-based BTMS technology has been recognized as one of the most promising solutions. Compared to traditional air and liquid cooling systems, PCM cooling technology exhibits superior cooling performance due to its large latent heat and efficient heat dissipation capabilities, while also eliminating the need for additional pump power consumption. Therefore, in-depth research on PCM cooling technology is of significant academic and practical value for enhancing the effectiveness and safety of power battery thermal management. This study investigates the effects of thermal conductivity, melting point, and thickness of composite phase change materials (CPCM) on the transient temperature of cylindrical lithium-ion battery 18650 under high discharge rates (5C) through numerical simulations. The findings indicate that: (1) The thermal conductivity significantly impacts the melting rate of CPCM and the surface temperature of the battery; increasing thermal conductivity beyond 3.5 W/(m·K) shows negligible improvement in cooling effectiveness. (2) The selection of melting point directly affects the battery temperature rise; CPCMs with lower melting points effectively prolong melting time, maintaining the battery temperature close to the melting point. (3) The thickness of CPCMs also significantly influences thermal management; in this case, a thickness of 3-4 mm has been proven adequate to meet the thermal regulation requirements of the battery under harsh conditions. This research provides a theoretical basis for the application of CPCM in battery thermal management.