Regulation of Interfacial Polarization and Local Electric Field Strength Achieved Highly Energy Storage Performance in Polyetherimide Nanocomposites at Elevated Temperature via 2D Hybrid Structure

Abstract Dielectric materials with excellent high‐temperature energy storage performances are urgently demanded in advanced electronic market. However, the sharply reduced energy storage capabilities caused by conduction loss impede the applications of polymer‐based nanocomposites at harsh environments. In this work, the 2D hybrid structure fillers of boron nitride nanosheets‐titanium dioxide (BNNSs‐TiO 2 ), where TiO 2 nanoparticles tightly wrap around the 2D BNNSs, are fused with polyetherimide (PEI) forming polymer nanocomposite films. The finite element simulation and experiment results indicate that the hybrid structure 2D BNNSs‐TiO 2 can effectively regulate local electric field strength and interfacial polarization, facilitating the enhancement in energy storage properties. Accordingly, the composite film delivers a superior discharged energy density (≈4 J cm −3 ) and charging/discharging efficiency (≈90%) at 150 °C, better than recently discussed high‐temperature pristine polymer and their composite films. This contribution offers a feasible idea to explore reliable dielectric capacitors at high temperature.