High energy storage density in high-temperature capacitor films at low electric fields

High-power applications, particularly in electromagnetic catapults, electric vehicles, and aerospace, necessitate the use of polymer dielectrics that demonstrate reliable performance in high-temperature environments. This study focuses on synthesizing three distinct morphologies of innovative wide-bandgap high-dielectric materials—hydroxyapatite (HAP). By conducting a combination of experiments and Multiphysics finite element simulations, a comprehensive comparison was made regarding the properties exhibited by three polyimide (PI) composites: PI/sea urchin-like HAP, PI/spherical HAP, and PI/rodlike HAP. The incorporation of high-surface-area spherical HAP or high aspect ratio rodlike HAP introduces intricate and convoluted growth paths for electric tree formation within the PI matrix, thereby augmenting the energy storage density ( U e ) at elevated temperatures ( U η > 90% = 4.82 J/cm 3 , U η > 80% = 6.11 J/cm 3 , U η > 70% = 8.73 J/cm 3 , at 150 ℃). The incorporation of HAP increases the dielectric constant ε r to a maximum value of 4.96 in pure PI matrices, enabling the resulting PI/HAP composites to achieve remarkable values for both U e (4.82 J/cm 3 ) and η (92.4 %) even under low electric field ( E ) conditions (350 MV/m). The PI/HAP composite film demonstrates high energy storage density under low E , offering an innovative solution for energy storage applications in film capacitors operating in high-temperature environments.