Energy storage properties of P(VDF-TrFE-CTFE)-based composite dielectrics with uniform and gradient-doped boron nitride nanosheets

Dielectric capacitors play an important role in advanced electronic and power systems such as portable electronic devices, hybrid electric vehicles and electronic weapon systems, and the improvement of energy storage density will have a positive effect on reducing the volume and weight of equipment. Here, a series of single-layer dielectrics with boron nitride nanosheets (BNNSs) uniformly dispersed and multilayer dielectrics with BNNSs showing a positive gradient distribution (PGD) and inverse gradient distribution (IGD) in the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P[VDF-TrFE-CTFE]) matrix were prepared by high-speed electrospinning and hot press technology. It is found that the best performance is observed inthe lowest interlayer gradient component in both PGD and IGD composite dielectrics. However, the performance of PGD is better than that of IGD, and the 3-5-3 multilayer dielectric in the positive gradient structure has the best electrical performance. Its maximum energy storage density of the 3-5-3 composite dielectrics is 12.93 J/cm³ at the applied electric field of 380 kV/mm. The above research results show that the gradient structure design plays an important role in optimising the breakdown strength and energy storage characteristics of composite dielectrics.