Electron-Trapping Molecular Engineering in Cycloolefin Copolymer Dielectrics for High-Temperature Capacitive Energy Storage

High-temperature dielectric capacitors require polymer dielectrics with simultaneously high energy density, low dielectric loss, and excellent thermal reliability. However, conventional high-temperature polymers generally suffer from severe conduction losses, while cycloolefin copolymer (COC), despite its excellent thermal stability and low dielectric loss, exhibits limited breakdown strength (Eb) that restricts its energy storage capability. Herein, an all-organic molecular blending strategy is proposed by incorporating anthrone (AT) molecules into a COC matrix to regulate charge transport and enhance dielectric performance. The introduced AT molecules regulate carrier transport through their electron-accepting characteristics and favorable energy-level alignment, facilitating electron trapping and suppressing carrier migration. Consequently, the optimized AT1.0 composite achieves enhanced Eb of 654 MV m–1 and a discharge energy density (Ud) of 5.13 J cm–3 at 150 °C while maintaining an ultrahigh charge–discharge efficiency (η) above 95%. Furthermore, the composite film exhibits excellent high-power discharge capability, stable cycling performance over 5 × 104 cycles, and outstanding large-area uniformity. This work demonstrates a molecular blending strategy for enhancing the energy storage performance of COC-based polymer dielectrics by regulating charge transport, providing an effective approach for developing high-temperature capacitive energy storage materials.