Thermal Management of Lithium-ion Battery Modules for Electric Vehicles

This research is particularly focused on studying thermal management of lithium-ion (Li-ion) battery modules in electric vehicles by using active, passive and hybrid active-passive methods. The thermal behavior prediction of batteries is performed by a novel electrochemical-thermal model. Different approaches such as single- and double-channel liquid cooling, pure passive by using phase change materials (PCM), and hybrid active-passive thermal management systems are investigated. Various cooling system configurations are examined to expand understanding of effect of each approach on the battery module thermal responses during a standard driving cycle. It is observed that the temperature distribution of Li-ion batteries is strongly influenced by the electrical and thermal operating conditions and simplified bulk models cannot precisely predict the thermal behavior of these batteries. Additionally, the PCM-based passive systems show advantages such as compactness and simplicity over the active liquid cooling systems. However, these systems suffer from non-uniform temperature distribution due to inherently low thermal conductivity of organic PCM. An effort has been made to enhance the thermal conductivity of a paraffin wax by adding various carbon-based nanoparticles. The results revealed that the thermal conductivity of the base PCM can be improved by about 11 times when using 10% mass fraction of graphite nanopowder. The heat transfer in the nano-enhanced PCM samples showed that the presence of nanoparticles drastically repress the natural convection in the melted nanocomposites. Among the battery thermal management systems studied, the air assisted hybrid cooling system provides the best temperature distribution uniformity in the module while keeping the batteries temperature within the safe limits. Furthermore, this work attempted to recognize the most influential parameters on the temperature distribution in the battery module. It is seen that the thickness of cooling plates and PCM layers in active and hybrid systems has a significant effect on the thermal behavior of the batteries.