Researchers developed a flexible polyetherimide copolymer film that achieved a discharged energy density of 7.34 J/cm³ at 200 °C, according to a study published in Nature Communications. The material maintained an energy efficiency above 90% while operating under an electric field of 680 MV/m. Those figures represent a 395.95% improvement over the unmodified pristine film.
Engineers regularly face a trade-off between electrical polarization and breakdown strength when creating flexible dielectrics for energy storage. To overcome that limit, the research team synthesized polyetherimide copolymers with tunable hydrogen bond donors and acceptors. The design introduced polarizable hydroxyl groups to increase the dielectric constant and expand hydrogen bond donor density. This network strengthened intermolecular interactions, elevating breakdown strength and thermal stability.
Chemists on the project also added bulky trifluoromethyl substituents into the molecular chains. These larger groups widened the physical spacing between individual polymer chains. Enlarging the interchain distance suppressed charge transport across the material, which prevented leakage currents from degrading performance at elevated temperatures.
Minhao Yang, Haoran Sun, Junjie Wang, and colleagues at North China Electric Power University conducted the research alongside scientists from Tsinghua University, Beijing University of Chemical Technology, and East China Normal University. The Analytical Instrumentation Center of North China Electric Power University provided material characterizations for the experiments.
China's Smart Grid-National Science and Technology Major Project funded the research under grant 2025ZD0808403. Additional backing came from the National Natural Science Foundation of China through grants 52577025, 52527803, and T2222025. The journal received the submission on June 28, 2026, accepted it on August 24, 2026, and published the peer-reviewed paper on September 4, 2026.
