Tailoring Poly(Styrene-co-maleic anhydride) Networks for All-Polymer Dielectrics Exhibiting Ultrahigh Energy Density and Charge–Discharge Efficiency at Elevated Temperatures

Polymer film capacitors have been widely used in electronics and electrical power systems due to their advantages of high power densities, fast charge–discharge speed, and great stability. However, the exponential increase of electrical conduction with temperature and applied electric field substantially degrades the capacitive performance of dielectric polymers at elevated temperatures. Here, the first example of controlling the energy level of charge traps in all-organic crosslinked polymers by tailoring molecular structures that significantly inhibit high-field high-temperature conduction loss, which largely differs from current approaches based on the introduction of inorganic fillers, is reported. The polymer network with optimized crosslinking structures exhibits an ultrahigh discharged energy density of 7.02 J cm⁻³ with charge/discharge efficiencies of >90% at 150 °C, far outperforming current dielectric polymers and composites. The charge-trapping effects in different crosslinked structures, as the origins of the marked improvements in the high-temperature capacitive performance, are comprehensively investigated experimentally and confirmed computationally. Moreover, excellent cyclability and self-healing features are demonstrated in the polymer film capacitors. This work offers a promising pathway of molecular structure design to scalable high-energy-density polymer dielectrics capable of operating under harsh environments.