Thermal Uniformity of Pouch-Type Lithium Ion Batteries with NCM Cathode Materials under Different Operating Conditions

With the advantages of flexible size and high energy density etc., pouch-type lithium ion battery cells with large capacity have been found more and more applications in electric vehicles. For these large-scale battery cells, thermal uniformity is vital for their safety and cycle life. To be specific, temperature gradients are expected to cause different degradation rates of active materials in different areas, which is possible to cause early failure or even fire and explosion of the battery cell. Thus, it is necessary to illustrate the batterie’s thermal uniformity in detail under different operating conditions. This work investigated the thermal uniformity of two 36 Ah pouch-type NCM/C battery cells with different sizes using both the thermal imaging method and thermoelectric effect method with K-type thermocouples. Experimental results show that there is an obvious temperature gradient on the surface of the pouch-type battery cell. The temperature of the positive electrode is significantly higher than other regions, which denotes that cooling the electrodes could a possible and effective solution for battery thermal management system. The current rare and direction can both have obvious influence on the temperature gradients of the cells. Moreover, pouch-type cells with different sizes present differences in temperature uniformity. The sample in a long strip shape showed better performace in thermal uniformity than that in a near square shape. The battery thermal behavior presented in this work provides excellent data for the validation of electro-thermal models and could be helpful for the optimization of battery cells and the design of their thermal management systems.