Significantly Boosted High-Temperature energy storage of polyetherimide film induced by BaTiO3/Al2O3/Ag composites nanofibers

Polymer dielectrics are essential materials for next − generation power systems. However, they suffer from low energy density and poor breakdown performance at high temperatures, which restricts their application in high-temperature fields. The BaTiO₃/Al₂O₃/Ag nanofibers (BT/AO/Ag NFs) were fabricated via electrospinning as nanofillers to boost the high-temperature energy storage of polyetherimide (PEI) composites. Experiments and finite electric field simulations demonstrate that combining high permittivity BaTiO₃, highly insulating Al₂O₃, and metallic Ag improves the dielectric permittivity and breakdown strength of PEI composites at high temperatures. Remarkably, the composite film incorporating merely 0.3 wt% BT/AO/Ag NFs achieves an ultra − high energy density of 9.047 J cm⁻³ at 200 ℃, representing a 147 % enhancement compared to pure PEI and surpassing most polymer composites filled with alternative nanofillers. Furthermore, this composite exhibits outstanding charge–discharge cycling stability (>100,000 cycles at 200 MV m⁻¹) and superior power density (>1.145 MW cm⁻³) at 200 ℃, positioning it as an ideal candidate for high-temperature capacitor applications. The work indicates that this nanofiber architectural design not only provides an effective strategy for developing high-temperature dielectric composites, but also shows great potential in next − generation dielectric capacitors.