Ultra-High Capacitance Energy Storage Enabled by Weakening the π–π Stacking Effect in Novel Polynorbornene

The increasing demand for high-power-density energy storage in advanced pulsed power systems necessitates polymer film capacitors exhibiting superior energy storage capabilities. Aromatic dielectric polymers, such as polyimide and polycarbonate, despite extensive research, exhibit a significant surge in conductivity loss under high electric fields due to their strong π – π stacking interactions. Herein, a novel norbornene polymer (PNB2APS) is prepared, and its strong π – π stacking interactions are effectively weakened through copolymerization with adamantylated norbornene (NBAd), thereby yielding a novel copolymer with ultrahigh breakdown strength (BDS) and enhanced discharge energy efficiency ( η ) under high electric fields, as demonstrated both experimentally and theoretically. A discharge energy density ( U d ) of 23.5 J cm −3 is achieved at 1000 MV m −1 , while maintaining U d = 15 J cm −3 even when η exceeded 90%, surpassing the energy storage performance of state-of-the-art commercial polymers. The film exhibits cost-effectiveness and facile processability, with high homogeneity and outstanding capacitance stability (>100 000 cycles), providing a practical pathway for scalable polymer dielectrics in high-performance electrical energy storage applications.