Design and Thermal Performance Analysis of a Novel Dual-Layer Cascade Phase Change Battery Thermal Management System

Lithium-ion Battery, as the power source of electric vehicles, pose a threat to the safety and life of the battery when thermal runaway occurs during operation. Although PCM thermal management systems are widely used in Li-ion batteries, the commonly utilized single-stage phase change material systems are not suitable for variable ambient temperatures. This paper presents a novel dual-layer Cascade phase change material (PCM) battery thermal management system suitable for variable ambient temperatures. Utilizing the NTGK semi-empirical formula within the multi-scale multi-dimensional (MSMD) model, it is coupled with the melting and solidification model. The single-stage PCM systems and the cascaded PCM systems are analyzed respectively. The maximum temperature of the cell, the variation rule of temperature difference and its correlation with the phase change of PCM are investigated. In addition, the optimal arrangement of PCM in the cascade system is determined, and the thermal performance of the stepped PCM system under different AT and battery discharge rates is studied. The results indicate that higher ambient temperatures and discharge rates lead to increased battery heat generation. For single-stage phase change systems, better cooling effects are achieved when the PCM phase change temperature is closer to the ambient temperature. Additionally, at a given ambient temperature and PCM configuration, higher battery discharge rates result in more pronounced cooling effects. The occurrence of the maximum temperature inflection point and the temperature difference peak coincides with the moment when the PCM layer absorbs latent heat. For the cascade system, arranging the PCM layers from inner to outer based on the decreasing trend of phase change temperature yields optimal results. This system is suitable for batteries operating within the temperature range of 298.15 K to 310.15 K, with its cooling efficiency surpassing that of the single-stage system when the environmental temperature reaches 310.15 K. In two ranges of ambient temperature (298.15 K-301.15 K and 301.15 K-310.15 K), the cooling effect of the system is better with the increase of ambient temperature and discharge multiplication.