RESUMO
Polymer-based dielectric capacitors play a notable part in the practical application of energy storage devices. Graphene oxide (GO) nanosheets can improve the dielectric properties of polymer-based composites. However, the breakdown strength will greatly reduce with the increase of GO content. Hence, the construction of sandwich structure can enhance the breakdown strength without reducing the dielectric constant. Herein, single-layered and sandwich-structured poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) nanocomposites with low content of GO nanosheets (<1.0 wt%) are prepared via employing a straightforward casting method. Compared with the single-layered composites and pure P(VDF-CTFE), the sandwich-structured composites exhibit comprehensively better performance compared. The sandwich-structured composite with 0.4 wt% GO nanosheets show an excellent dielectric constant of 13.6 (at 1 kHz) and an outstanding discharged energy density of 8.25 J cm-3at 3400 kV cm-1. These results demonstrate that the growth of the dielectric properties is owing to 2D GO nanosheets and the enhancement of breakdown strength due to the sandwich structure. The results from finite element simulation provide theoretical support for the design of high energy density composites.
RESUMO
Na0.5Bi0.5TiO3 (NBT) ceramic is the promising dielectric material for energy storage devices due to its high maximum polarizability and temperature stability. However, its low breakdown strength limits its application. Here, we prepared 0-3 type composite 0.45Na0.5Bi0.5TiO3-0.55Sr0.7Bi0.2TiO3/x wt % AlN (NBT-SBT/xAlN) to increase the breakdown strength. The effects of the various AlN contents on the phase composition, microstructures, dielectric, and energy storage properties of NBT-SBT were systematically discussed. The result showed that the enhanced energy storage properties were obtained by introducing AlN particles. The NBT-SBT/6AlN composite ceramics showed a high breakdown strength of 360 kV/cm, large energy density of 5.53 J/cm3, and energy efficiency of 90%. Meanwhile, the excellent frequency (10-500 Hz) and temperature stability (25-125 °C) were exhibited with the fluctuation of energy storage within 9% and energy efficiency more than 87%, suggesting that the 0-3 composite NBT-SBT/xAlN is a candidate dielectric material for the dielectric energy storage.
RESUMO
Recent developments in various technologies, such as hybrid electric vehicles and pulsed power systems, have challenged researchers to discover affordable, compact, and super-functioning electric energy storage devices. Among the existing energy storage devices, polymer nanocomposite film capacitors are a preferred choice due to their high power density, fast charge and discharge speed, high operation voltage, and long service lifetime. In the past several years, they have been extensively researched worldwide, with 0D, 1D, and 2D nanofillers being incorporated into various polymer matrixes. However, 1D nanofillers appeared to be the most effective in producing large dipole moments, which leads to a considerably enhanced dielectric permittivity and energy density of the nanocomposite. As such, this Review focuses on recent advances in polymer matrix nanocomposites using various types of 1D nanofillers, i.e., linear, ferroelectric, paraelectric, and relaxor-ferroelectric for energy storage applications. Correspondingly, the latest developments in the nanocomposite dielectrics with highly oriented, surface-coated, and surface-decorated 1D nanofillers are presented. Special attention has been paid to identifying the underlying mechanisms of maximizing dielectric displacement, increasing dielectric breakdown strength, and enhancing the energy density. This Review also presents some suggestions for future research in low-loss, high energy storage devices.