Network‐Structured All Organic Composite for High‐Temperature Capacitive Energy Storage

ABSTRACT

High‐temperature dielectric polymers are promising for advanced power electronics and electrical systems but often suffer from thermally activated charge transport and breakdown under harsh operating conditions. Here, we demonstrate that high‐loading low‐molecular‐weight oligomeric arylene ether urea (O‐EEU) can regulate charge transport in polyetherimide (PEI) through network‐mediated matrix partitioning. At the optimized loading, O‐EEU forms an O‐EEU‐rich network within the PEI matrix, converting the originally continuous PEI phase into localized compartments. This compartmentalized architecture induces charge‐path segmentation and spatially confines carrier motion, thereby suppressing leakage conduction and delaying the formation of continuous breakdown channels. Meanwhile, the polar urea in O‐EEU contributes to additional dipolar polarization. As a result, the optimized PEI/O‐EEU composite exhibits a dielectric constant of 4.22 and a breakdown strength of 797 MV m ⁻¹ at 150°C, giving rise to a discharged energy density of 9.05 J cm ⁻³ with a charge–discharge efficiency above 90%, along with excellent cycling stability and self‐clearing capability. This work converts high‐loading oligomer incorporation from a risky aggregation induced by conventional filler inclusion into an internal matrix‐partitioning strategy for charge‐transport regulation, unlocking the door for rational design of high‐temperature dielectric energy storage.