Overcoming polarization-breakdown trade-off via hydrogen bonding-modulated molecular stacking in high-temperature high-energy-density flexible dielectric

Flexible dielectrics suffer from an inherent polarization-breakdown trade-off. Herein, we propose a hydrogen bonding-modulated molecular stacking strategy to improve high-temperature capacitive energy storage performance. A series of polyetherimide copolymers with tunable hydrogen bond donors and acceptors was synthesized. Highly polarizable hydroxyl groups boost dielectric constant and increase hydrogen bond donor density. The constructed hydrogen bonding network strengthens intermolecular interactions, thermal stability, and breakdown strength. Bulky trifluoromethyl substituents enlarge interchain spacing and suppress interchain charge transport. Ultimately, the copolymer with optimal molecular stacking delivers a maximum discharged energy density of 7.34 J/cm3 with efficiency exceeding 90% at 680 MV/m and 200 °C, representing a 395.95% improvement over the pristine film and outperforming most reported flexible dielectrics. This intrinsic molecular modulation route offers a facile design strategy for designing high-temperature high-energy-density flexible dielectrics. The authors propose a molecular stacking strategy regulated by hydrogen bonding to enhance the high-temperature capacitive energy storage performance of polymer dielectrics. This special structural design achieves an energy density of 7.34 J/cm3 and an efficiency of 90% at 200 °C.