Superior High-Temperature Energy Storage Performance in Multilayer PEI-Based Nanocomposites via Functional Fillers Integration

Dielectric polymer capacitors are widely used in electronic power systems, pulse power systems, and hybrid vehicles due to their excellent charging-discharging rates as well as ultrahigh power density. However, a grimness challenge is to achieve both high energy storage density (Ue) and high efficiency (η). Herein, we report a three-layer structured polymer-based nanocomposite, in which the outer insulation-layers are composed of boron nitride nanosheets (BNNSs) with polyetherimide (PEI), while Ba0.6Sr0.4TiO3 nanofibers (BSTNFs) with PEI as the inner polarization-layer. The three-layer structure effectively combines the advantages of each functional layer, offering high interfacial polarization and high breakdown strength, and consequently leading to an enhanced Ue of the nanocomposites. Consequently, an ultrahigh Ue of 20.96 J/cm3 accompanied with an outstanding η of 95.74% can be obtained in the optimized composition with the inner layer containing 5 vol% BSTNFs, which is 4.78 times as high as that of the pure PEI film (4.38 J/cm3). Notably, the nanocomposite obtains a satisfactory high-temperature performance even under harsh environments (Ue = 10.84 J/cm3, η > 80%, 150 °C), thereby manifesting a substantial application potential. Therefore, this study offers a novel and promising route to high-performance polymer-based dielectrics.