Polyimide Nanocomposites Filled with SiO₂ Nanoparticles of Different Sizes for High-Temperature Energy Storage

Most polymer-based film capacitors experience severe degradation in electrical performance in high-temperature environments, making thermal stability a crucial factor for their stable use. This study prepared nanocomposites of polyimide mixed with three different particle sizes of nano-SiO 2 particles using in situ polymerization methods. The experiment showed that filling the composites with different particle sizes of nano-SiO 2 nanoparticles suppressed the leakage current density and significantly increased the breakdown field strength under high-temperature conditions. The nanocomposite containing 3 vol % 20 nm-SiO 2 /PI nanoparticles with high specific surface area exhibited excellent electrical performance, with a discharge energy density of 5.34 J cm –3 at 550 MV m –1 and 150 °C and an efficiency of 86.3%. The composite material also had an optical bandgap of 2.59 eV. Finite element simulations proved the accuracy and reasonableness of the experimental data. This study further verifies that high specific surface area nanofillers can indeed maximize the electrical performance of the composites, providing an example of the role of ultrafine nanoparticles in enhancing the harsh environment energy storage properties of polymers.