Superior high-temperature energy-storage performance of multilayer PEI-based nanocomposites via functional filler integration

Abstract

Dielectric polymer capacitors are widely used in electronic power systems, pulse power systems, and hybrid vehicles owing to their excellent charging–discharging rates and ultrahigh power density. However, it remains a challenge to simultaneously achieve high energy storage density (U_e) and high efficiency (η). Herein, we report a three-layer structured polymer-based nanocomposite, in which the outer insulation layers were composed of boron nitride nanosheets (BNNSs) with polyetherimide (PEI), while the inner polarization-layer comprised Ba_0.6Sr_0.4TiO₃ nanofibers (BSTNFs) with PEI. The three-layer structure effectively combined the advantages of each functional layer, offering high interfacial polarization and high breakdown strength, consequently leading to an enhanced U_e of the nanocomposites. Consequently, an ultrahigh U_e of 20.96 J cm⁻³ accompanied with an outstanding η of 95.74% could be obtained in the optimized composition with the inner layer containing 5 vol% BSTNFs, which was 4.78 times higher than that of a pure PEI film (4.38 J cm⁻³). Notably, the nanocomposite demonstrated a satisfactory high-temperature performance even under harsh environments (U_e = 10.84 J cm⁻³, η > 80%, and 150 °C), thereby demonstrating substantial application potential. Thus, this study offers a novel and promising route towards high-performance polymer-based dielectrics.