Decoupling thermal stability and insulation in dielectric polymers via donor-acceptor rearrangement

Polymer dielectrics with enhanced thermal stability and electrical insulation are urgently needed for capacitive energy storage applications in electric power systems. There is a persistent challenge to break the contradictory correlation between high heat resistance and low electrical conduction in polymers. Here, we employ benzyl-induced crosslinking to rearrange short-range structural units in polyimide chains, reducing electrical conduction loss. The designed polymer exhibits an electrical conductivity more than 3 orders of magnitude lower than that of commercial heat-resistant polymers, while its glass transition temperature (Tg) increases from 236.31 °C (for polyetherimide) to 289.72 °C. Consequently, a discharged energy densities of 6.38 J cm−3 and 3.04 J cm−3, with charge-discharge efficiencies above 90%, are achieved at 200 °C and 250 °C, respectively, demonstrating among the best in all-organic dielectric polymers. This work presents a feasible approach to break the adverse correlation between thermal stability and electrical insulation in polyimide materials. Polymer dielectrics have potential in capacitive energy storage applications, but achieving the required thermal stability and electrical insultation is challenging. Here, the authors report a method to rearrange short-range structural units within polyimide chains to give improved properties.