Synergistic Molecular Engineering and Crosslinking Topology for High‐Temperature Energy Storage in All‐Organic Dielectrics

This work presents an all‐organic polymer dielectric that combines high‐energy density with excellent high‐temperature endurance. To address the significant loss in polyetherimide (PEI) at high temperatures, a synergistic strategy is employed. This strategy involves the introduction of trifluoromethyl (CF 3 ) groups into the polymer backbone alongside a crosslinking design, achieving precise control over chain spacing and local ordering. The CF 3 groups increase intermolecular distance and suppress entanglement through steric hindrance and electrostatic repulsion. The resulting local ordered structures, working in concert with the introduced deep charge traps, effectively inhibit carrier migration. The constructed crosslinked networks further stabilize this tailored microstructure and enhance polarization properties. The optimized FPEI/AQD film achieves a discharged energy density ( U e ) of 8.95 J cm −3 with 90% efficiency ( η ) at 150 °C, reaching a peak U e of 11.00 J cm −3 , and retains 6.85 J cm −3 at 200 °C. Meanwhile, the FPEI/0.3 wt% HTP composite maintains 3.89 J cm −3 at 250 °C. This work, by implementing a collaborative molecular and crosslinking topology design, achieves precise control over chain spacing and local ordering, thereby providing a novel strategy for developing advanced high‐temperature dielectric materials.