Enhanced energy density of PVDF-HFP/CCTO nanocomposites induced by aspect ratio fillers

Abstract

Dielectric materials with high energy density have a wide range of applications in high-performance capacitors, sensors, brakes, spacecraft, and electric stress control devices. Adding inorganic filler in the polymer matrix is an effective way to increase the energy density of the polymer materials, the characteristics of composites and inorganic filler with high dielectric constant and high breakdown strength of polymer materials. However, the aggregation and phase separation of inorganic fillers in the polymer matrix is still the key obstacle to the practical application of the composites. Here, we develop a novel strategy for the growth of high aspect ratio calcium copper tianate nanofibers (CCTO-NFs) with electrospinning method, and then the high energy density nanofiber composites materials are fabricated using polydopamine (PDA) modify high aspect ratio CCTO-NFs in a poly(vinylidene fluoride-co hexafluoropropylene) (PVDF-HFP) matrix. The microstructure, dielectric properties, and energy storage density of the composites were studied. It was found that the two types of fillers were dispersed homogeneously in the PVDF-HFP matrix. The dielectric constant of the composites filled by CCTO nanofiber is large than CCTO nanoparticles at the same content. Stronger interfacial polarization mainly determined the dielectric properties that we observed on PVDF-HFP/CCTO-NFs composites. Moreover, a relatively low dielectric loss and a low conductivity achieved is attributed to the high aspect ratio of fillers and excellent compatibility of the CCTO nanofiber and PVDF-HFP matrix. Furthermore, when the content of filler was 10 wt.%, the discharged energy density of PVDF-HFP/CCTO NFs composites (1.508 J/cm3) is 4.17 times higher than that of PVDF-HFP/CCTO NPs composites (0.214 J/cm3). Such significant enhancement could be attributed to the combined effects of the surface modification and large aspect ratio of the CCTO-NFs. This work may provide a route for using the surface modified CCTO nanofibers to enhance the dielectric energy density in ceramic-polymer nanocomposites.