Enhanced High‐Temperature Capacitive Energy Storage in Topology‐Regulated Semi‐Aromatic Polyimides by Triazine Polarized Nodes and Helical Transport Barriers

ABSTRACT Polymer dielectrics operating under extreme environments require increasingly higher demands on electrical insulation performance. Polyimide (PI), one of the most promising candidates for high‐temperature energy‐storage dielectrics, tends to form charge‐transfer complexes (CTCs) under high temperatures and high electric fields, which promotes carrier migration and increases dielectric loss. In this work, by introducing 3,9‐Bis[2‐(3,5‐diamino‐2,4,6‐triazaphenyl) ethyl]‐2,4,8,10‐tetraoxaspiro[5.5]undecane (DTI) into semi‐aromatic polyimide (SPI), a topology‐regulated SPI‐co‐DTI network was constructed. The electron‐deficient triazine units in DTI can induce local electrostatic‐potential heterogeneity and polarized transport barriers. The helical configuration of DTI further disrupts the continuity of interchain coupling and blocks charge‐transport pathways. SPI‐co‐0.5%DTI achieves a discharged energy density ( U d ) of 8.79 J cm −3 with an efficiency ( η ) above 90% at 150°C and 780 kV mm −1 . At 200°C, SPI‐co‐0.5%DTI still maintains a high U d of 5.93 J cm −3 , which is 103% higher than that of SPI at the same conditions. This work provides a new design concept and paradigm for developing high‐performance polymer dielectrics for harsh‐environment applications.