High field properties and energy storage in nanocomposite dielectrics of poly(vinylidene fluoride-hexafluoropropylene)

Abstract

Poly(vinylidene fluoride) (PVDF) has generated interest for use in electrical energy storage, mostly due to its high dielectric constant compared to other polymers. There still exist challenges, such as its high energy losses, that have prevented large scale commercialization of PVDF-based capacitors, but progress is continuously being made. In this paper we explore a promising route to improve the energy storage performance of PVDF, through a synergy of HFP comonomers and of kaolinite clay nanofillers. This study shows that the addition of these high aspect ratio fillers to poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] copolymers does not increase the polar phase and, consequently, these composites exhibit markedly enhanced dielectric properties at high electric fields. Specifically, strained films of these composites exhibit reduced high field losses, markedly increased breakdown strength and, thus, large recoverable energy density values, in the range of 19 J/cm3.

Crystal structure transformation and dielectric properties of polymer composites incorporating zinc oxide nanorods

“…Figure 4 displays the XRD patterns of both neat P(VDF-HFP) and P(VDF-HFP) nanocomposites. It is clearly seen that there are four peaks which correspond to the α(100), α(020), α(110), and α(021) crystal plane [5]. A slight difference in the intensity of each peaks is observed between the neat P(VDF-HFP) and the nanocomposite with 10 wt% ZnO nanorods.…”

“…It is reasonable to study the patterns of P(VDF-HFP) in reference to the standard patterns of PVDF [3,5] . Figure 4 displays the XRD patterns of both neat P(VDF-HFP) and P(VDF-HFP) nanocomposites.…”

“…The five absorption curves are almost of the same shape, which means the introduction of ZnO nanorods does not change the absorption behavior of P(VDF-HFP) heavily. The absorption peaks at 762.1 cm -1 and 795.8 cm -1 can be ascribed to the α phase and the absorption peak at 840.5 cm -1 is belongs to the β phase [2,5] . And only when the content of ZnO nanorods reaches as high as 20 wt% or further, the absorption at 840.5 cm -1 shows up, which is in consistent with results of XRD measurement.…”

“…For example, Giannelis et al [2] studied a composite based on P(VDF-HFP) and clays and found that the introduction of organically modified clays promotes the transformation from α phase to β phase. Randall et al [5] investigated a composite made by P(VDF-HFP) and kaolinite clay nanofillers, and their studies suggest that the incorporation of high aspect ratio fillers do not favor the formation of polar phase. All those studies indicate that the fillers play an indispensible role in the crystallization process of P(VDF-HFP).…”

“…The chain conformation of α phase and β phase are trans-gauche-trans-gauche' (TGTG') and tans-trans-trans-trans (TTTT) respectively. Through the β phase is not a stable phase compared with the α phase, it still raises a lot of research interest, since it has an impressive effect on the piezoelectric and pyroelectric properties [5] . To date, numerous fillers, such as nanoclay [6,7] , carbon nanotubes [8] , and graphene sheets [9,10] have been used as an effective method for the forming of β phase PVDF.…”