Molecular Design of Polymer Dielectrics With Local State Traps for High‐Temperature Energy Storage

ABSTRACT Polymer dielectrics exhibit significant advantages in dielectric capacitors due to their high breakdown strength, thermal stability, and excellent processability. However, polyetherimide (PEI) exhibit a significant increase in conduction loss at elevated temperatures due to a strong intramolecular charge transfer effect, severely limiting energy storage performance. This work proposes a design strategy based on molecular structural regulation to suppress conduction loss. Functional diamine units are introduced into the PEI backbone to construct local state traps, while regulating the suppression of charge transport by local hole traps and local large conjugated dihedral angle. The results demonstrate that PEI copolymer films with 4,4'‐Oxydianiline (ODA) can achieve optimal regulation between local hole traps and local large conjugated dihedral angle, thereby introducing the deepest local state traps and significantly suppressing charge transport. At 200 °C, PEI‐ODA film exhibits an exceptional discharge energy density of 3.82 J/cm 3 with an efficiency exceeding 90%, while maintaining high reliability of 50 000 cycles. This research presents a molecular design strategy for high‐temperature applications, providing significant insights for the development of high‐temperature polymer dielectric for high‐power electronic systems.