Enhanced thermal performance of a hybrid battery thermal management system with sandwich-structure phase change materials at a high discharge rate

To ensure the working temperature environment of batteries at an ultra-high discharge rate of 5 C, this work proposes a hybrid battery thermal management system (BTMS) with thermoelectric coolers (TECs), phase change materials (PCMs), and heat pipes. The sandwich-structure PCMs are also introduced to alleviate the temperature difference between the inner and outer batteries. According to the numerical results predicted by a developed transient electric-fluid-thermal multiphysics model, it is found that the BTMS with sandwich-structure PCMs enables superior thermal performance compared to the BTMS with single PCMs. The inner layer PCMs with a higher thermal conductivity compared to the outer layer help to lower the battery maximum temperature and temperature difference, but an oversized thermal conductivity may even amplify the temperature difference. Besides, the lower the melting point of outer layer PCMs, the lower the battery maximum temperature and temperature difference are. An increase in the TEC input current can further reduce the maximum temperature but deteriorate the temperature difference, and the working range of 0.75 A-1.25 A is suggested. Through a comparison of different cases, the combination of PCM1 for the inner layer and PCM4 for the outer layer features the best thermal performance, with a maximum temperature of 316.78 K and a temperature difference of 4.09 K at an optimal input current of 1.25 A for the TEC. This research demonstrates the feasibility of sandwichstructure PCMs in lowering the battery temperature difference at extreme conditions.