Evaluation of heat dissipation performance for automotive batteries with micro/ nano-enhanced phase change materials (MN-PCMS)

Lithium-ion batteries and lithium-iron batteries are the most commonly used lithium batteries in electric vehicles. Heat dissipation performance strongly affects the output capacity and safety of lithium batteries. There are many ways to dissipate heat from batteries, including air-cooling, water-cooling, vapor compression cycle cooling, phase change materials (PCMs) cooling, or a combination of the above methods. Lower output horsepower vehicles such as electric motorcycles or work vehicles often use wax-based phase change materials as a cooling medium. The advantage of using PCMs as a cooling medium for lithium battery packages is that when the operating temperature of the lithium batteries exceeds the phase change temperature, the PCMs will absorb the melting heat from the solid state and then transform into a liquid state. Liquid PCMs can transfer the heat generated by the lithium batteries to the outer casing via liquid convection heat transfer for heat dissipation. When the lithium batteries are not in use, the PCMs will gradually turn into a solid state when the temperature drops below the phase change temperature. Solid-state lithium battery packs will not leak. Safety can be greatly improved whether in storage or transportation. Generally, wax-based PCMs have the advantages of high phase change heat and low price. However, general paraffin wax (PW) has low thermal conductivity and most have melting points higher than the most suitable operating temperature for lithium batteries. Therefore, this study added different concentrations of boron nitride (BN) and aluminum nitride (AlN) into soybean wax (SW) to prepare micro/ nano-enhanced phase change materials (MN-PCMs). BN and AlN have superior insulation properties and thermal conductivity, which can improve the thermal conductivity of PCMs and reduce the melting temperature, making them more suitable for use in PCMs for heat dissipation of lithium batteries. The phase change temperature and phase change heat (melting heat) of the MN-PCMs prepared in this study were measured using a differential scanning calorimeter (DSC) to evaluate the feasibility of practical application in lithium batteries for heat dissipation.