Aramid dielectric co-polymer: from molecular engineering to roll-to-roll scalability for high-temperature capacitive energy storage

Abstract

Aromatic polymer films with high glass transition temperatures (T_g) exhibit superior thermal stability, making them ideal for high-temperature dielectric capacitors in advanced electrical and electronic systems. However, the leakage current can be intensified at high temperatures due to stronger π-electron delocalization, leading to energy loss and degrading capacitive performance. Here, we present a poly sulfonated aramid (PSA) derived from aramid by molecular engineering, with T_g > 300 °C. Sulfone groups with a non-planar structure are introduced to break strong π–π conjugation and subsequently suppress intramolecular charge transfer. Moreover, their large dipole moments contribute to a high dielectric constant. To suppress intermolecular charge transfer, organic small molecules of triptycene (TE) are filled at an optimized content, breaking π–π stacking among PSA chains. The activation energy for trapped carriers is further increased, while the hopping distance is shortened. The PSA/TE all-organic film achieves an energy density (U_d) of 5.71 J cm⁻³ at an efficiency exceeding 90% and a maximum U_d of 9.03 J cm⁻³ at 150 °C. Additionally, sulfone groups also aid self-healing by generating more gaseous products during pyrolysis. A roll-to-roll production line is established for continuously fabricating large-scale and high-quality PSA-based films, allowing for industrial potential for high-temperature capacitive energy storage.