Multilayer BOPET dielectric film with internal double electron barrier for high temperature applications

With the continuous development of modern electronic and power equipment, practical applications in harsher environment call for film capacitors with higher temperature resistance. Here, we designed a multilayer film including two outer layers of biaxially oriented polyethylene terephthalate (BOPET), two inorganic layers of boron nitride nanosheets (BNNSs), and an intermediate epoxy layer. Due to the blocking effect of the BNNSs layer, the propagation of the breakdown path is hindered, which improves the breakdown strength of the film. Meanwhile, the carrier transport in the medium is effectively hindered, reducing the conduction loss of the composite film. As a result, the optimized multilayer composite film had a high discharged energy density of 8.76 J/cm3, maintaining a high charge-discharge efficiency of 95% at 25 °C, while remarkable values of 7.04 J/cm3 and 73% were obtained even at 150 °C, which showed prominent improvements compared with BOPET. Thus, it turns out to be a promising strategy of fabricating high temperature dielectric films.