Cascade phase change based on hydrate salt/carbon hybrid aerogel for intelligent battery thermal management

Abstract

Working performance of Li-ion battery in electric vehicle will degrade under cold environment. Excess heat of battery can be stored via melting of calcium chloride hexahydrate (CCH) and then released to warm battery when environment temperature drops. Formation of composite can improve thermal conductivity and stability of pristine CCH but reduce loading content. Meanwhile, energy stored in phase change material (PCM) is utilized in low efficiency as homogeneously filled PCM releasing heat uncontrollably. Therefore, there is an urgent need to achieve efficient heat storage and controllable heat release by designing an intelligent phase change system. In this research, MOF-derived carbon (MOF-C)/graphene oxide (GO) hybrid aerogel was proposed to load CCH. PCM loading content could be enhanced by the synergistic effect between MOF-C and GO, while thermal conductivity of PCM composite could be improved due to the formation of hybrid aerogel three-dimensional network. Furthermore, CCH@MOF-C/GO structures with gradient freezing point (FP) were designed to build a cascade phase change system to release heat efficiently, in which CCH with high FP triggering heat release of adjacent PCM with low FP. Comparing with the homogeneously filled PCM, warming time was prolonged and discharge capacity of battery was enhanced successfully under cold environment by utilizing the cascade PCM.