Ultrahigh β-phase content poly(vinylidene fluoride) with relaxor-like ferroelectricity for high energy density capacitors

Abstract

Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations. Herein, a facile process of pressing-and-folding is proposed to produce β-poly(vinylidene fluoride) (β-phase content: ~98%) with relaxor-like behavior observed in poly(vinylidene fluoride) with high molecular weight > 534 kg mol−1, without the need of any hazardous gases, solvents, electrical or chemical treatments. An ultra-high energy density (35 J cm−3) with a high efficiency (74%) is achieved in a pressed-and-folded poly(vinylidene fluoride) (670-700 kg mol−1), which is higher than that of other reported polymer-based dielectric capacitors to the best of our knowledge.

Multiscale understanding of electric polarization in poly(vinylidene fluoride)-based ferroelectric polymers

“…PVDF crystallizes into the a-phase when cooled from the melt. The b-phase is usually obtained after post-treatments of the as-formed a-phase, like solid-state drawing, 8 solid-state pressure deformation 10 and/or electric field poling (4500 kV mm À1 ). 8 Poling at relatively low electric fields (B170 kV mm À1 11,12 ) can only transform the a-phase into the d-phase.…”

Role of protic ionic liquid concentration in proton conducting polymer electrolytes for improved electrical and thermal properties

“…The absorption coefficients K 840 and K 763 are taken to be 7.7×10 4 and 6.1×10 4 cm 2 mol −1 [25,27]. The individual phase fraction of β and γ-phases from the total polar phase is calculated using: where I 1275 and I 1234 are the absorbencies at 1275 cm −1 (β phase) and 1234 cm −1 (γ-phase), respectively [28].…”

Enhanced Energy Storage Characteristics in PVDF-Based Nanodielectrics With Core-Shell Structured and Optimized Shape Fillers

“…where E and D are the applied electric field and displacement, respectively [2]. Specifically, for linear dielectrics:…”