Rational Design And Optimization Of Dielectric Polymer Nanocomposites With A High Energy Storage Density

With the development of human society,the demand for energy is gradually increasing.As an advanced form of energy utilization,electric energy is more and more widely applied in many fields.It is difficult to improve the energy storage density of the film capacitor.Therefore,in this paper,we mainly discuss the high-performance polymer-based dielectric composites,and the main results is shown as follows:(1)Fluorine rubber(PPA)with high permittivity was introduced to improve the permittivity of polypropylene(PP),and it is found that PPA is dispersed uniformly in PP matrix,which leads to the improved permittivity and energy density of PPA/PP composite film.PPA/PP with 35 wt%filler shows a permittivity of 2.8 at 102 Hz,while its energy density at 200 MV/m reaches 1.21 J/cm3,which is 2.2 times that of the pure PP film.(2)Barium titanate was added to the PP matrix to improve the permittivity.In order to further improve the electrical breakdown strength of the composites,the third-phase:rubber filler was added.The results demonstrates that both SEBS and EPDM significantly improve the dispersion of nanofillers in polymer matrix,the dielectric properties,breakdown strength and energy storage characteristics of nano-composites.When the rubber content is 10 wt%,the dielectric constant is up to 3.1,and the breakdown strength of the composite film increases from 277 MV/m to 341 MV/m(SEBS/BT/PP)and 315 MV/m(EPDM/BT/PP),respectively.It should be noted that the energy storage density at 200 MV/m reaches about 1.2 J/cm3,when the rubber content is 15 wt%.(3)Polyurethane(TPU)was chemical grafted onto BT nanoparticles successfully to prepare core-shell structure high-permittivity nanofiller(TPU@BT),It is found that the addition of TPU@BT could improve the dielectric properties of PVDF matrix.The permittivity of TPU@BT/PVDF composite with 12 wt%filler was as high as 13.5 at 102 Hz,which is 1.5 times higher than that of pure PVDF.In addition,the energy density is 1.7 J/cm3.(4)High-k filler with core-shell structure was successfully prepared by grafting diisocyanate(MDI)on the surface of BT nanoparticles,which improves the dispersibility and compatibility of BT in PVDF matrix.In addition,MDI@BT nanoparticles promote the dielectric and energy storage properties of the composites.The permittivity of composite with 12 wt%MDI@BT reaches 13.7(102 Hz),while pure PVDF is only 8.2,and the energy density increases to 2.0 J/cm3.Moreover,compared with TPu@BT,MDI@BT nanoparticles can effectively hinder the deterioration of charging and discharging efficiency for PVDF composites.