| Higher standards for the demand for clean energy have been imposed by the progress and development of the times.Polymer dielectric capacitors are widely used as clean energy devices in new energy vehicles,electronic communications,high-power pulse power supplies,and other important fields.Nonetheless,possessing both high polarization and insulating properties is highly difficult for polymers.As the matrix,this study used the ferroelectric polymer poly(Vinylidene Fluoride-Trifluoroethylene)P(VDF-Tr FE)and the liner Polymer Polycarbonate(PC)to resolve the issue of strong coupling between the dielectric constant and the breakdown fields strength.Adjust the relative positions of the two to prepare an all-organic composite dielectric with a sandwich structure and a multilayer structure,use the multilayer interface to suppress the carrier migration,and improve the dielectric and energy storage properties.First,solution casting method and electrospinning method were used to create pure PC and P(VDF-Tr FE)dielectrics.Positive sandwich structure and anti-sandwich structure composite dielectrics were created using PC as the outer and inner layers.Adjust the thickness of P(VDF-Tr FE)as the volume fraction variable while keeping the overall thickness of the composites.With temperature,the properties of the dielectric composites were observed to change significantly.Rendering the degree of interface polarization of the positive sandwich composites higher with regard to the anti-sandwich composites,the increase in temperature increased the activation energy of the composite dielectric.The energy storage efficiency reached 84.87%at the electric field intensity of 520 k V/mm and the positive sandwich structure composite dielectric could attain the discharge energy density of 10.89 J/cm~3 when the volume fraction of P(VDF-Tr FE)was 23.34 vol%.The anti-sandwich composite dielectric showed a breakdown field strength,however,significantly decreases as P(VDF-Tr FE)volume fraction rises,and its energy storage properties are inferior to those of the positive sandwich composite dielectric.The random breakdown simulation shows that the positive sandwich structure composite dielectric is more effective in suppressing the conductive path and improving the breakdown field strength than the anti-sandwich structure composite dielectric.Further enhancing the insulation properties of the composite dielectrics,the number of layers based on the sandwich structure were increased to five,to develop multilayer composite dielectrics.Illustrating a trend of initially increasing and subsequently decreasing,the polarization strength of the multilayer composite dielectric and breakdown field strength were the same as that of the sandwich composite dielectric,when the PC was in the outer layer with an increase in the P(VDF-Tr FE)volume fraction.When PC is in the inner layer,although the breakdown strength and polarization strength of multilayer structure composite dielectrics are significantly higher than that of anti-sandwich structure composite dielectrics,they still maintain a downward trend.Under the electric field intensity of 500 k V/mm and660 k V/mm,the energy storage efficiency of 85.37%and 87.79%and the discharge energy density of 11.634 J/cm~3 and 9.16 J/cm~3were attained respectively.Multilayer structure composite dielectric can significantly reduce carrier injection at the electrode in comparison to sandwich structure,and it also has a higher interface charge accumulation and stronger interlayer coupling.Besides,the electric field distortion was found to have improved effectively,with the reasonable regulation of the electric field distribution of the composite,with the multilayer structure.The strength of the electric field for every layer of the dielectric was found to be significantly higher than that of P(VDF-Tr FE)and PC.In conclusion,this paper adopts the linear/ferroelectric multilayer structure design strategy,which uses the layering effect and the stacking advantage layer by layer to improve the interaction between interfaces,gradually slow down carrier migration rates in different layers,while enhancing the energy storage and dielectric properties of the polymer dielectrics. |
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