Diatom-based biomass composites phase change materials with high thermal conductivity for battery thermal management

Battery thermal management systems (BTMs) are a significant strategy for controlling the operating temperature of lithium-ion batteries (LIBs) used in electric vehicles (EVs). A promising approach for mitigating the risk of battery exceeding the highest operating temperature is the utilization of composite phase change materials (CPCMs) in BTMs, which have the potential to be applied in EVs. In this study, a vacuum impregnation process was employed to prepare the biomass-based CPCMs (PPE-0, PPE-10, PPE-30 and PPE-50), consisting of diatomite as a supporting matrix, expanded graphite (EG) as an additive, and polyethylene glycol (PEG) as the phase change media. The PPE-10 exhibits an enhancement of melting enthalpy (116.81 J/g) and crystalline enthalpy (118.44 J/g). Meanwhile, the thermal conductivity of PPE-10 is 1.203 W/m·K, which is higher than PEG and PPE-0 by 4.02 times and 2.18 times, respectively. Furthermore, the battery modules with prepared CPCMs were carried out the charge and discharge processes at 1C and 2C discharge rates. The results illustrate that the battery modules with PPE-10 show excellent thermal management capability, which maintains the temperature below 60 °C during a 2C discharge rate. Consequently, this study provides a novel insight into developing biomass-based CPCMs with high thermal conductivity to enhance the safety of battery modules in EVs.