Engineering hierarchical interfaces in high-temperature polymer dielectrics for electrostatic supercapacitors.

Dielectric capacitors are pivotal elements in advanced pulsed power devices and high-voltage, high-capacity power electronic converters, crucial for efficient energy storage. However, a major challenge remains the significant reduction in energy density and charge-discharged efficiency of dielectric polymers under high temperatures, primarily due to heightened electrical conduction losses. This study introduces a universal approach of heterojunction interface engineering in polyethersulfone (PESU) composites, aimed at improving capacitive performance across a broad temperature range. The introduction of one-dimensional heterojunction BaTiO 3 @Al 2 O 3 nanofibers with large aspect ratios could enhance both the dielectric constant ( ε r ) and breakdown strength ( E b ). Specifically, the creation of hierarchical interfaces increases the trap density and energy levels for mobile charges, effectively reducing conduction losses and improving E b under high-temperature conditions. Consequently, the PESU-3 vol% BaTiO 3 @Al 2 O 3 nanocomposite achieves an excellent energy density of 7.3 J cm -3 with over 90% retention at 150 °C and 550 MV m -1 . Finite element simulations further confirm that the heterojunction structure of BaTiO 3 @Al 2 O 3 nanofibers effectively inhibits the growth of breakdown paths. This work demonstrates that hierarchical interface engineering offers a powerful strategy to enhance capacitive performance in dielectric polymer composites under harsh conditions.