Sandwich-structured polymers with electrospun boron nitrides layers as high-temperature energy storage dielectrics

Most dielectric polymers have unsatisfactory energy storage characteristics at high temperature. In this work, hexagonal boron nitride (h-BN) layers with different thickness playing roles in thermal conduction and carrier blocking are designed and transferred on both sides of polycarbonate (PC) films. They existing in the aggregation status of h-BN plates are fabricated via electrospinning technology. It is found that the thermal conductivity of the composite films is improved due to the existence of h-BN layers. The composite film with layer thickness of 1 μm (BN-1) has low leakage current density, high breakdown strength and excellent high-temperature energy storage characteristics. The energy storage density of BN-1 is 5.52 J/cm3 under 500 MV/m electric field at 100 ℃, which is 15.10% higher than that of pure PC. At the same time, the density and efficiency stability of BN-1 are superior to pure PC in the temperature range of RT-100 ℃. Finally, the operation status of composite capacitor in practical applications is simulated by using the dynamic data concerning thermal conductivity and leakage current of composite films at different temperatures. The outstanding operation status in composite capacitor indicates that a promising, scalable and affordable route to high-temperature dielectric is provided.