Rui Wang,Congzhen Xie,Shoukang Luo,Huasong Xu,Bin Gou,Jiangang Zhou,Hao Yang
Polymer-based dielectric materials with high energy storage performance have become an important part of electric power and electronic systems. But due to the low intrinsic dielectric constant of polymers, it is usually needed to mingle high dielectric constant nanofillers to improve their dielectric properties. However, the addition of nanoparticles often results in higher dielectric loss and lower breakdown strength. Herein, using a simple method of surface modification of BaTiO3, silica and polydopamine are coated on the surface of BaTiO3, significantly improving the dielectric properties of the polymer. Meanwhile, the composite with a sandwich structure is prepared by using BaTiO3@SiO2@PDA/PVDF as the central layer and pure PVDF as the two outer layers, achieving an ultrahigh breakdown strength (633 MV/m). The sandwich-structured composite with 1 wt % BaTiO3@SiO2@PDA has the highest discharge energy density (15.4 J/cm3). The simulation results reveal that the sandwich structure not only acts as an interface carrier barrier but also optimizes the electric field concentration inside the composite, which reduces the probability of electric breakdown. This work can broaden the way for dielectric films to be used in the field of high energy density, and the modification strategy can also provide ideas for other fields.
Rui Wang,Congzhen Xie,Bin Gou,Huasong Xu,Shoukang Luo,Yan Du,Jiangang Zhou,Hao Yang
Flexible nanocomposite dielectrics with high dielectric constant and discharge energy density have broad application prospects in the field of energy storage. However, dielectrics with high dielectric constant tend to have a high dielectric loss. Herein, we prepared a dielectric composite material with ultra-high discharge energy density by modifying the interface between nanoparticles and poly(vinylidene fluoride-co-hexafluoropropylene) (P[VDF-HFP]). After coating a shell of insulating amorphous SiO 2 (~7 nm) outside the barium titanate (BT), the electric field concentration and current density inside BT particles can be significantly reduced. In addition, coating the SiO 2 shell with a polydopamine (PDA) shell (~7 nm) not only enhances the interface interaction between the nanoparticles and the polymer matrix, but also can form lots of microcapacitors in the composite. As a result, an ultra-high discharge energy density of 13.78 J/cm 3 at the expense of relatively inconspicuous efficiency (~59.8%) in the BT@SiO 2 @PDA/P (VDF-HFP) with 2.5 wt% loading has been achieved under 460 kV/mm. This is mainly attributed to the increases of dielectric constant from 12.1 to 14.2 and the relatively low dielectric loss (0.086) at 100 Hz. Moreover, compared with the pure P (VDF-HFP) (400 kV/mm), the breakdown voltage of the composite with 2.5 wt% loading is surged to 460 kV/mm, which benefited from the hindrance of nanoparticles on carrier migration at low content. This work has realized a thin-film dielectric with ultra-high discharge energy density through a novel design of the nanoparticle structure, providing a theoretical direction for the development of polymer dielectric capacitors.
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