Breaking the adverse correlation between thermal stability and electrical insulation in polymer dielectrics by rearranging the donor and acceptor units

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 existing polymers. Here, we demonstrate a strategy for the effective rearrangement of short-range structural units within polyimide (PI) polymer chains through the preferred layer packing structure. This adaptable reorganization of monomeric units potently inhibits charge carrier transmission between the donor (diamine) and acceptor (dianhydride) moieties in PI chains, significantly reducing electrical conduction loss. The electrical conductivity of the designed polymer (named TPEI) is more than 3 orders of magnitude lower than that of commercial heat-resistant polymers. At the same time, this distinctive strategy is found to significantly improve the heat resistance of the modified polymer, with its glass transition temperature (T _g ) rising from 236.31°C for pure PEI to 289.72°C for the TPEI. Consequently, ultrahigh 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 ℃ and 250 ℃, 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 PI materials.