Enhancing high field dielectric properties of polymer films by wrapping a thin layer of self-assembled boron nitride film

Polymer dielectrics play an important role in modern electric power systems because of their ultrahigh power density, low cost, and lightweight. Current high-k polymers represented by poly(vinylidene fluoride) (PVDF) based ferroelectric polymers suffer from the high energy loss as well as the low temperature level. To overcome the conduction induced high loss, in present work, a BN thin layer fabricated from an oil-water self-assembly method is transferred on poly(vinylidene fluoride-chlorotrifluoroethyelen) (P(VDF-CTFE)) films. The BN layer with high bandgap may significantly depress the dielectric loss of polymer films, and reduce the charge injection in the films at both elevated temperature and electric field. That is responsible for the dramatically increased breakdown strength, energy density, discharge efficiency and even temperature level of P(VDF-CTFE). The optimized sample (c.a. BP-3) possesses a high energy density of 12.95 J/cm(3) at 525 MV/m at ambient temperature. At 80 degrees C, BP-3 sample has an energy density of 6.38 J/cm(3), which is nearly 8 times that of pristine P (VDF-CTFE) (0.78 J/cm(3)). This work offers a promising strategy to improve the breakdown strength and the dielectric performance of polymeric dielectrics.