Crystal Orientation Effect on Electric Energy Storage in Poly(vinylidene fluoride-co-hexafluoropropylene) Copolymers

Abstract

By using different preparation and processing methods, poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF−HFP)] films with different crystal orientations were fabricated. Anisotropic dielectric properties and different electric energy storages were observed in these films. When the PVDF crystals in a film oriented with their c-axes perpendicular to the applied electric field, they exhibited large polarizability because the CF2 dipole moments were randomly distributed in a plane parallel to the electric field. As a result, high dielectric constant and high electric energy density were achieved. On the contrary, when the crystal c-axes in a film oriented parallel to the electric field (or the CF2 dipole moments perpendicular to the electric field), polarization became difficult. Consequently, low dielectric constant and low electric energy density resulted. The anisotropic polarizability was also displayed at high electric fields as evidenced by the difference in the remnant/maximum polarization and the dipole switching field for different crystal orientations. These results provide us a guidance to achieve optimal crystalline morphology in PVDF random copolymer films for high electric energy storage applications.

A comparison of two different methods for formation of the beta phase in nanocomposites based on vinylidene fluoride-hexafluoropropylene copolymer

“…The X-ray diffractograms were analyzed with respect to the standard X-ray diffractograms of PVDF [13], since the small quantity of HFP in the VDF-HFP copolymer (15 mol %) has not changed significantly the symmetry of the crystal lattice compared to that of the homopolymer PVDF [14]. The peaks at 2θ = 17.7 [15,16], 18.4 [15][16][17][18], 19.9 [15,16] and 26.6° [15,16,19] correspond to 100, 020, 110 and 021 diffractions of the PVDF α-phase while the peaks at 2θ = 20.2, 20.6 [18], 20.7 [15,19] and 20.8° [15-17, 19, 20] -up to 110 and 200 β -phase diffractions.…”

Crystal structure transformation and dielectric properties of polymer composites incorporating zinc oxide 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.…”

“…Specially, P(VDF-HFP) exhibits high chemical resistance and high flexibility as a result of the presence of HFP. Additionally, it is more interesting that the introduction of HFP does not change the crystalline structure while mediating the degree [3,4] . In other words, the copolymer P(VDF-HFP) exhibits almost the same crystal structure as PVDF.…”

Polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN)/carbon nanotube nanocomposites for energy storage and conversion

“…Moreover, PAN could provide a few important characteristics towards polymer electrolytes which could not be derived from PVDF [12]. PVDF has been extensively studied as an important crystalline polymer for a broad range of applications, including, but not limited to, transducers [13], non-volatile memories [14,15], and electrical energy storage [16,17].…”