Preparation And Dielectric Energy Storage Properties Of P(VDF-HFP) Based Sandwich Composite

Polymer dielectrics have the advantages of high breakdown strength,good processability and high flexibility,so they are widely used in various industries.The reason for their low energy density is the extremely low dielectric constant.Therefore,it is necessary to fill high dielectric ceramic materials into the polymer.Although the dielectric constant of the composite material will be improved,due to the huge difference in performance between the ceramic material and the polymer,it will inevitably produce the problem of poor dispersion of the filler or poor interface compatibility.In addition,the electric field concentration of the filler in the polymer matrix will become higher,leading to premature breakdown of the composite material.Although many researchers modified the filler to fill the polymer matrix,it could avoid a substantial reduction in breakdown strength to a certain extent,but the effect was limited.Therefore,in this paper,composite dielectric films with high energy storage density are prepared by using the properties that each layer of the sandwich structure can be endowed with different functions(dielectric layer or breakdown layer).Firstly,a shell layer of PF30 polyfluorosiloxane was coated on BT by“thiol-ene click”reaction to prepare BT@PF30 functional fillers.SEM,TEM and XPS were used to characterize BT@PF30 in detail,which successfully proved the preparation of BT@PF30core-shell structure.The aim is to improve the dispersion of BT filled with P(VDF-HFP)and the interface compatibility between BT and P(VDF-HFP),to make the electric field distribution in the dielectric layer more uniform,and the dielectric constant increases from6.47 to 9.19(@1k Hz)of pure P(VDF-HFP).At the same time,pure P(VDF-HFP)is used as a breakdown layer to effectively prevent the decrease of breakdown strength(only 20 MV/m is lost).The energy storage density of sandwich structure composite film under 460 MV/m achieves the high energy storage density of 10.41 J/cm~3.In order to further improve the energy storage density of the composite film,BNNSs with high breakdown strength is introduced into the middle layer of the composite film,hoping that the breakdown strength of the composite film can be improved.BNNSs was obtained by liquid phase stripping method from h-BN.AFM,TEM and other testing methods were used to prove that BNNSs was prepared.BNNSs is a two-dimensional material with high band gap(～6 e V).BNNSs can effectively block the development of electrical branches in the matrix.After 0.5wt.%BNNSs was introduced into the interlayer,the breakdown strength increased from460MV/m to 580MV/m,and the energy storage density further increased from 10.41 J/cm~3 to15.75 J/cm~3.In this paper,the sandwich structure composite film with high energy storage density is obtained by using the controllable performance of each layer of the sandwich structure,which can be used as a reference for the future dielectric research.