Ultra-High Capacitive Energy Storage Density at 150 °C Achieved in Polyetherimide Composite Films by Filler and Structure Design.

Polymer dielectrics are crucial for electronic communications and industrial applications due to their high breakdown field strength (E), fast charge/discharge speed, and temperature stability. The upcoming electronic-electrical systems pose a significant challenge, necessitating polymeric dielectrics to exhibit exceptional thermal stability and energy storage capabilities at high temperatures. Here, ultra-high dielectric constant (ɛ) and charge/discharge efficiency (η) of 0.55Bi(NaK)TiO-0.45(BiSr)TiO (BNKT-BST) ceramics are prepared by the solid-phase reaction method and added to polyetherimide (PEI) to form BNKT-BST/PEI nanocomposites with various structures. The findings indicate that the sandwich-structured BNKT-BST/PEI nanocomposite achieves the highest discharged energy density (U) of 7.7 J cm with η of 80.2% when the E is 650 MV m at 150 °C. This is primarily due to the incorporation of BNKT-BST nanoparticles and the multilayer structure design, which significantly improves the composite's ɛ and E. Additionally, the sandwich-structured composites show excellent cycling stability at 500 MV m and 150 °C, with U of ≈ 4.7 J cm and η greater than 90%. The research presents nanocomposites with high energy storage density and excellent stability, crucial for the practical application of polymer dielectrics in high-temperature environments.