Preparation And Electrical Properties Of Poly(vinylidene Fluoride)-Based Composites

High performance energy storage materials are very important in advanced electronic and pulsed power systems.Polymer dielectric is considered as a promising energy storage material,compared with inorganic ceramic dielectric,which has higher dielectric strength and stronger flexibility.However,due to its low intrinsic dielectric constant and ordinary ferroelectric properties,the energy storage capacity of the original polymer is limited.In order to obtain a new idea of high energy storage density material,the microstructure of inorganic filler phase and multilayer structure of PVDF have been exploited.A new method of preparation of high energy density materials was proposed.The 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT)is a perovskite ceramic,which has good with ferroelectric hysteresis characteristics.This paper has prepared BZT-BCT nanoparticles(BZT-BCT NPs)by sol-gel and BZT-BCT nanofibers(BZT-BCT NFs)by electrospinning.Based on these,BZT-BCT NPs/PVDF and BZT-BCT NFs/PVDF single layer composite films were prepared by solution coating method,their dielectric properties and energy storage characteristics were studied.The research results show that the one-dimensional BZT-BCT NFs owns an excellent performance.Under 10 Hz,the dielectric constant of 10 vol.% BZT-BCT NFs/PVDF is up to the 17.33.The breakdown field strength of 2.5 vol.% BZT-BCT NFs/PVDF composite reached at 340 kV/mm,the energy storage density reached nearly 7.8 J/cm3,and the charge discharge efficiency remained at about 50%.Then,the paper designed three different sandwich structure composites.The BN was introduced as middle layer filling phase,which has excellent thermal conductivity,insulating property and low loss.In order to prepared BZT-BCT NFs-PVDF/Fe3O4@BNNSs-PVDF/BZT-BCT NFs-PVDF sandwich-structure composite,Fe3O4@BNNSs-PVDF(Fe3O4@BN-P)as the middle layer and BZT-BCT NFs-PVDF(B-P)as the outer layer.At the same time,B-P/BN-P/B-P and P/Fe3O4@BN-P/P two sandwich-structure composites also prepared.The results showed that the B-P/Fe3O4@BN-P/B-P sandwich structure showed good characteristics.At 100 Hz,the dielectric constant of B-P/5 vol.% Fe3O4@BN-P/B-P reaches the maximum value of 17.At 350 kV/mm applied field,the storage density of B-P/5 vol.% Fe3O4@BN-P/B-P reaches the maximum of 8.9 J/cm3.