Ultrahigh energy density in high-temperature polymer dielectric reinforced by bilayer nanocoating

Next-generation electrical and power electronic systems necessitate polymer dielectrics with high energy densities and high-temperature applicability. However, such ever-increasing performance demands result in exponential increases of leakage electrical conduction, which is fundamentally associated with thermally and electrically assisted charge injection and transport mechanisms. Here, we report a substantial improvement in high-temperature energy storage properties for polymer dielectrics with a bilayer nanocoating. Two-dimensional boron nitride and montmorillonite nanosheets were coated on the polymer surface, showing a synergetic effect on trapping and dissipating the hot carriers injected from electrodes. We obtain an ultrahigh discharged energy density of 5.5 J/cm³ with an efficiency exceeding 90 % at 150 °C. This bilayer nanocoating strategy provides a generalizable approach for designing high-performance polymer dielectrics via interfacial engineering.