Excellent high-temperature energy storage performance of polymer dielectrics through the synergistic action of conjugation effect inhibition and dipole modulation

High-temperature polymer dielectrics with efficient energy storage are essential for modern power electronics, but their narrow bandgap and restricted dielectric constant contribute to low energy density and efficiency at high temperatures. In order to address this issue, a high-temperature polymer (Parylene C) with both a wide bandgap and a high dielectric constant has been developed using conjugate effect confinement and dipole modulation strategies. Non-conjugated vinyl groups were introduced into the aromatic backbone to discourage conjugation while maintaining thermal stability. Simultaneously, highly polar chlorine atoms were added to the aromatic ring to enhance dipole moments and increase the dielectric constant. The resulting polymers exhibit high discharged energy density (U_e) and high discharging efficiency at both room and elevated temperatures. Notably, under classical operating conditions (150 °C, 200 MV m⁻¹), Parylene C exhibits a U_e of 1.2 J cm⁻³, which is more than twice that of most commercially available high-temperature polymers (∼0.5 J cm⁻³), while also demonstrating excellent cycling stability. By balancing the contradiction between bandgap and dielectric constant through a molecular design strategy, this study achieves high energy storage at elevated temperatures and offers a novel approach for developing high-energy density, low-dielectric loss and high-temperature resistance polymers.