Significantly improving dielectric and energy storage properties via uniaxially stretching crosslinked P(VDF-co-TrFE) films

Abstract

Recently, tuning the normal ferroelectric performance of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-co-TrFE)) to either relaxor ferroelectric or anti-ferroelectric behavior by confining the relaxation of ferroelectric crystal domains physically or chemically has attracted considerable interest to achieve high discharged electric energy density (U e ) and low energy loss (U l ) for energy storage applications in high pulse capacitors. To improve the dielectric and energy storage properties as well as reduce the energy loss induced by the ferroelectric relaxation of P(VDF-co-TrFE), unsaturation containing P(VDF-co-TrFE) films were uniaxially stretched after crosslinking with peroxide in this work. P(VDF-co-TrFE) containing unsaturation was synthesized via controlled hydrogenation and dehydrochlorination of commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)). The properties of the films obtained were characterized with differential scanning calorimetry (DSC), X-ray diffraction (XRD), dielectric constant and electric displacement-electric field (D-E) hysteresis loop measurements. Compared with the as-cast and as-crosslinked films, the stretched films exhibit a significantly enhanced dielectric constant, breakdown field (E b > 500 MV m À1 ) and U e but depressed energy loss. This could be attributed to the enhanced film quality, optimized crystalline properties, improved orientation uniformity of crystal domains as well as accelerated ferroelectric relaxation induced by the crosslinking and mechanical stretching. The best performance was achieved for the stretched film with a dielectric constant of 15 at 1 kHz, a relatively high U e of 17.5 J cm À3 and a low energy loss of about 30% at 575 MV m À1 .

Synergetic Enhancement of Permittivity and Breakdown Strength in All‐Polymeric Dielectrics toward Flexible Energy Storage Devices

“…Dielectrics, which are insulating materials with the ability of storage/dissipation energy in an applied electric field, play an important role in modern electronics and electrical systems including capacitors, transistors, and cables, etc . Specifically, capacitors with higher volumetric energy density are gaining more and more attentions of academics and industries as the rapid developments of smart electronic devices such as radio frequency identification tags, health monitoring sensors, smart cell phones, etc.…”

Investigation of perfluorinated proton exchange membranes prepared via a facile strategy of chemically combining poly(vinylphosphonic acid) with PVDF by means of poly(glycidyl methacrylate) grafts

“…The 1 H-NMR spectrum exhibited the characteristic multiplets centered at 2.91 and 2.28 ppm originating from the methylene groups in -CH 2 -CF 2 -CH 2 -CF 2 -CH 2 -CF 2 -and -CF 2 -CH 2 -CH 2 -CF 2 -sequences appearing in the normal head-to-tail (ht) and reversed tail-to-tail (tt) VDF additions [17][18][19]. The new multiple peaks at 6.0-6.5 ppm in alkaline treated PVDF correspond to the protons on the double bonds (−CH 2 -CF=CH-CF 2 -) after the elimination of HF from PVDF [47][48][49][50]. These peaks evidenced the formation of the double bonds (−CH 2 -CF=CH-CF 2 -) in the alkaline treated PVDF.…”

“…The structure of PVDF is dominated by the presence of VDF-VDF head-to-tail (ht) (−CH 2 -CF 2 -CH 2 -CF 2 -CH 2 -CF 2 -) sequences appearing between −92 and −96 ppm, and VDF-VDF tail-to-tail (tt) (−CF 2 -CH 2 -CH 2 -CF 2 -) structure appearing between −114 and −117 ppm [47,48,51]. Compared with PVDF, the new signals emerging at around −107 ppm in alkalined treated PVDF could be assigned to the F atoms in the double bond (−CH 2 -CF=CH-CF 2 -) units [47,48,52]. The same peaks at around −107 ppm (20) were also detectable in the spectrum of PVDF-g-PGMA (in Fig.…”

Structure change and energy storage property of poly(vinylidene fluoride-hexafluoropropylene)/poly (methyl methacrylate) blends

“…All the phase transitions and crystalline data are summarized in table. The crystallinity χ c of all the films are calculated using the formula χ c = ΔH/ΔH* × 100%, where the heat of fusion for perfect PVDF crystal ΔH* is about 104 J/g [23]. The melting temperatures T m of films decrease from 157.6 to 152.2°C with the increase of PMMA content (from 0 to 40%), and the crystallinity drops from 18 to 7.7%.…”