Spatial-conformational locking of π-conjugated pathways enables 150–200 °C polyimides capacitive energy storage

The fatal rise in electrical conduction at elevated temperatures (> 150 °C) fundamentally limits polymer dielectrics, collapsing both energy density ( U d ) and efficiency ( η ) through thermally activated π-electron delocalization. While conventional crosslinking stiffens matrices, it neglects the electronic-structural origin of leakage: continuous π-orbital overlap/π-conjugation pathways along polymer backbones. Here, we report a spatial-crosslinked molecular-level strategy to surgically disrupt conjugation pathways in polyimides. By incorporating phenylethynylphthalic anhydride (PEPA) as a spatial-conformational modulator, we force critical dihedral rotations between phenyl rings through steric repulsion. This intentionally distorts chain geometry, fragmenting extended π-networks into isolated segments, concurrently improving mechanical stiffness and intrinsically suppressing conduction loss (maintaining high η ). The synergy enables outstanding U d (4.89 J cm −3 at 150 °C; 2.11 J cm −3 at 200 °C) with η  > 90 %, exceeding conventional PIs' limits at 200 °C. These films also show exceptional stability (> 10 4  cycles) and solution processability for scalable fabrication. By addressing the electronic-structural root of conduction loss, this work establishes spatial-crosslinking as a general design paradigm for next-generation high-temperature dielectric polymers.