Fabrication of silicone-based gap filler for electric vehicles using magnesium oxide thermally conductive fillers

With the recent increase in demand for electric vehicles, high-performance battery systems have also come under scrutiny. As the internal temperature of batteries rises, it can lead to product degradation, fire, and explosion issues. Therefore, to effectively dissipate internal heat, there is a demand for Thermal Interface Materials (TIMs) in the form of composite materials, consisting of high-polymer materials and highly thermally conductive ceramic fillers. In this study, a silicone-based TIM containing high thermal conductivity fillers was prepared and investigated for various properties including thermal conductivity, density, and hardness. We prepared a TIM with a thermal conductivity of 7.4 W/m–K and a theoretical density of 3.27 g/cm³ by filling 83 vol% of MgO fillers, surface-treated with a silane coupling agent, and Al₂O₃ filler. As the content of ceramic fillers within the resin increased, the TIM's density also increased, forming internal thermal paths and enhancing thermal conductivity characteristics. Besides, as the hardness of TIM increased, reducing adhesion and resulting in increased thermal contact resistance, ultimately leading to a decrease in thermal conductivity. Using a Gap Filler-type TIM facilitates efficient heat transfer by minimizing thermal contact resistance. Based on these results, a low-density lightweight silicone-based TIM (gap filler) for electric vehicles is manufactured using hollow glass bubbles with a density of 0.38 g/cm³, achieving a thermal conductivity of 2.3 W/m–K and a density of 2.17 g/cm³.