Aromatic‐Free Polymers Based All‐Organic Dielectrics with Breakdown Self‐Healing for High‐Temperature Capacitive Energy Storage

High-temperature dielectric polymers are becoming increasingly desirable for capacitive energy storage in renewable energy utilization, electrified transportation, and pulse power systems. Current dielectric polymers typically require robust aromatic molecular frameworks to ensure structural thermal stability at elevated temperatures. Nevertheless, the introduction of aromatic units compromises electrical insulation owing to pronounced π─π interactions that facilitate electron transport and eliminate the breakdown self-healing property owing to their high carbon content. Herein, an aromatic-free polynorborne copolymer exhibiting electrical conductivity-two orders of magnitude lower than that of state-of-the-art polyetherimide-at elevated temperatures and high electric fields owing to its large bandgap (≈4.64 eV) and short hopping conduction distance (≈0.63 nm) is described. Density functional theory calculations demonstrate that the copolymer can effectively suppress the excitation of high-field valence electrons. Furthermore, the incorporation of trace semiconductors results in high discharge density (3.73 J cm^-3 ) and charge-discharge efficiency (95% at 150 °C), outperforming existing high-temperature dielectric polymers. The excellent electrical breakdown self-healing capability of the copolymer film at elevated temperatures further demonstrates its potential for use in dielectric capacitors capable of continuous operation under extreme conditions.