Tailoring interfacial electron scattering in aramid-based composite films for capacitive energy storage at 200 °C

Thin-film capacitors, utilized for capacitive energy storage, hold significant importance in modern power and electronic systems. To fulfill high-temperature demands, polymers with high glass transition temperatures are adopted for thin-film preparation. However, high-temperature energy density still suffers from exponentially increasing leakage currents. Here, we incorporate ZIF-8 metal-organic framework fillers in the matrix of poly ( m -phenylene isophthalamide) (PMIA) to prepare the composite films. ZIF-8 exhibits organic compatibility due to its organic ligands, and it owns self-stability, devoid of inducing the PMIA chain plasticization. Strong hydrogen bonds form between the amide groups in PMIA and imidazole rings in ZIF-8, optimizing the PMIA chain conformation with minimized free volume. Accompanied by electron scattering at the PMIA/ZIF-8 interfaces, leakage current is reduced by one order of magnitude. At a 0.3 wt% content, the film exhibits a breakdown strength of 688.9 MV·m −1 at 150 °C and 609.9 MV·m −1 at 200 °C. Furthermore, the polyhedron geometry of ZIF-8 intensifies interfacial polarization, yielding a high dielectric constant of 5.72 at 200 °C and 100 Hz, and a low dielectric loss confined by the hydrogen bonding network. These improvements achieve a maximum energy density of 12.88 J·cm −3 at 150 °C and 9.45 J·cm −3 at 200 °C, highlighting its potential for high-temperature energy storage.