Tailoring Poly(Styrene‐co‐maleic anhydride) Networks for All‐Polymer Dielectrics Exhibiting Ultrahigh Energy Density and Charge–Discharge Efficiency at Elevated Temperatures

with charge/discharge efficiencies of >90% at 150 °C, far outperforming current dielectric polymers and composites. The charge-trapping effects in different crosslinked structures, as the origins of the marked improvements in the high-temperature capacitive performance, are comprehensively investigated experimentally and confirmed computationally. Moreover, excellent cyclability and self-healing features are demonstrated in the polymer film capacitors. This work offers a promising pathway of molecular structure design to scalable high-energy-density polymer dielectrics capable of operating under harsh environments.