Designing high-energy-density all-organic flexible dielectric films from molecular structure to polymer cross-linking networks

Increasing the polarity of molecular chains is the key to achieving high energy density in polymers. However, the polarization capability of polymers is not merely an accumulation of monomer dielectric properties. A pressing need arises for a universal design concept to guide the development of all-organic dielectric films, extending from monomer molecular structure to the polymer cross-linking network. In this research, we have developed a flexible dielectric film with a high energy density. The reduction of rotational space hindrance for polar functional groups ensures the polymer's heightened polarity. Additionally, the staggered arrangement of ester groups and benzene rings, combined with cross-linking constraints, alleviates the decrease in insulation performance caused by the planar conjugation of benzene rings. Significantly, the adjustment of the cross-linking network effectively mitigates the high conduction and polarization losses associated with enhanced polarization. The reduced interchain spacing contributes to lowering the average charge mobility, thereby restricting charge movement. Surprisingly, the polymer film exhibits a high breakdown strength of 770 MV/m and an ultra-high discharge energy density of 16.7 J/cm³. This surpasses the levels observed in traditional polymer dielectric films, emphasizing the potential impact of molecular structure design and polymer cross-linking networks in advancing high-performance polymer dielectrics.