Construction of Multiple Hydrogen Bonding Networks to Enhance the Energy Storage Performance of PVDF/MG Composites

Electrostatic capacitors are indispensable components in energy storage devices. Polymer-based dielectric films are widely utilized in capacitors because of their low cost and excellent processability, whereas their low energy density (Ue) limits further advancements in the energy storage dielectric field. In this research, a linear methyl methacrylate-co-glycidyl methacrylate (MG) copolymer/ferroelectric poly(vinylidene fluoride) (PVDF) matrix is employed as the matrix by incorporating 2,5-dihydroxyterephthalic acid (DHTA), a small organic molecule with both carboxyl (−COOH) and hydroxyl (−OH) groups, as a filler, which constructs multiple hydrogen-bond (HB) cross-linking networks. The findings reveal that this small-molecule DHTA, which is rich in multiple polar groups, simultaneously enhances the overall polarity and breakdown strength (Eb) of the composite. The three-phase composite film with 0.4% DHTA showcases the maximum Ue of 23.2 J/cm3 at 640 MV/m accompanied by an efficiency of 71%, which is approximately 4.3 times that of the PVDF/MG composite (5.6 J/cm3 at 440 MV/m). The improvement of energy storage capability stems from the charge-trapping effect of multiple HB interactions, which is confirmed by experimental and simulation results. This study offers a highly effective approach for developing all-organic composite films that exhibit exceptional energy storage capabilities.