High-temperature polymer dielectrics with superior capacitive energy storage performance

Polymer dielectrics for high-temperature capacitive energy storage are extremely desirable in modern electronics and electrical systems. However, pure polymer dielectrics operating above 200 °C have yet not been reported. Here, we demonstrate a polymer dielectric polynorbornene-imide (PNI) exhibits excellent energy storage performances at 250 °C owing to simultaneous large optical bandgap (4.3 eV) and high glass transition temperature (265 °C) endowed by the full-carbon backbone and rigid side chain containing benzene ring and the imide group. Significantly, PNI delivers a maximum discharged energy density (Ud) of 6.04 J/cm3 at 200 °C and a Ud of 2.57 J/cm3 at 250 °C. More importantly, PNI exhibits a Ud above 90% efficiency of 2.8 J/cm3 at 200 °C, and 0.74 J/cm3 at 250 °C, outperforming reported all pure polymer dielectrics and polymer composites dielectrics so far. The excellent recycling stability, fast discharge capability and unique self-healing capacity enables it a promising candidate for capacitor films in industry. This work provides a new design strategy for polymer dielectrics under harsh environments.