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The thermophysical parameters and amount of composite phase change materials (PCMs) have decisive influence on the thermal control effects of thermal management systems (TMSs). At the same time, the various thermophysical parameters of the composite PCM are interrelated. For example, increasing the thermal conductivity is bound to mean a decrease in the latent heat of phase change, so a balance needs to be achieved between these parameters. In this paper, a prismatic LiFePO4 battery cell cooled by composite PCM is comprehensively analyzed by changing the phase change temperature, thermal conductivity and amount of composite PCM. The influence of the composite PCM parameters on the cooling and temperature homogenization effect of the TMS is analyzed. which can give useful guide to the preparation of composite PCMs and design of the heat transfer enhancement methods for TMSs.

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.

With the increasing frequency of fire incidents of electric vehicles, the safety of power batteries has attracted more and more attention. At present, the research on the safety of power batteries is mainly focused on fresh batteries. As the state of health of batteries deepens, how the safety of the battery evolves is not clear enough so far. This paper analyzes the external short-circuit safety of a NCM/C rectangular battery under different state of charges. The results show that when the cycle number is less than 800, the maximum temperature of the battery during short-circuit is below 130 °C. The main failure mode of the battery is bulging in volume or opening of the explosion-proof valve and there is no obvious regularity between the failure mode with the cycle life. However, when the cycle number reaches 1000, the battery goes into thermal runaway during the safety test.