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[Display omitted] • PVB additives were firstly introduced to the solid composite electrolytes (SCEs). • The SCE has a high lithium-ion transference number (t+ =0.72). • At 3C, a capacity of around 100 mAh g−1 was also achieved. All solid-state lithium-ion batteries (ASSLBs) are thought to benefit from using solid composite electrolytes (SCEs) to increase their energy density and safety. In this study, we firstly introduce the PVB additives to SCEs and prepared a SCE composed of a mixture of nanostructured MOFs (UiO-67), PVDF-HFP, PVB, and LiTFSI. Electrochemical characterizations of the SCEs (EIS, LSV, CV and battery test) were also conducted. The SCE UBP-2 (PVB:PVDF-HFP = 1:10) shows a high lithium-ion transference number (t Li + =0.72) and good ionic conductivity (3.27×10−4 S cm−1 at 60 °C). A symmetric Li cell with SCE UBP-2 can be continuously cycled at 0.1 mA cm−2 for more than 2500 h without experiencing a short circuit. The full cell (LiFePO 4 /UBP-2/Li) also maintained a high reversible discharge capacity of 154.9 mAh g−1 at 0.1C after 200 cycles at 60 °C. At 3C, a capacity of around 100 mAh g−1 was also achieved. This work might help to enhance the development of the forthcoming all solid-state batteries. [ABSTRACT FROM AUTHOR]

To further advance the application of flexible piezoelectric materials in wearable/implantable devices and robot electronic skin, it is necessary to endow them with a new function of antibacterial properties and with higher piezoelectric performance. Introducing a specially designated nanomaterial based on the nanocomposite effect is a feasible strategy to improve material properties and achieve multifunctionalization of composites. In this paper, carbon dots (CDs) were sensitized onto the surface of ZnO to form ZnO@CDs nanoparticles, which were then incorporated into polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) to obtain a multifunctional composite. On the one hand, the antibacterial property of ZnO was improved because CDs had good optical absorption of visible light and their surface functional groups were favorable for electrostatic adsorption with bacteria. Therefore, ZnO@CDs endowed the composite with an outstanding antibacterial rate of 69.1% for Staphylococcus aureus . On the other hand, CDs played a bridging role between ZnO and PVDF-HFP, reducing the negative effect of ZnO aggregation and interface incompatibility with PVDF-HFP. As a result, ZnO@CDs induced β-phase formation of 80.4% in PVDF-HFP with a d 33 value of 33.8 pC N -1 . The multifunctional device exhibited excellent piezoelectric and antibacterial performance in the application of energy harvesters and self-powered pressure sensors.

Battery safety calls for solid state batteries and how to prepare solid electrolytes with excellent performance are of significant importance. In this study, hybrid solid electrolytes combined with organic PVDF-HFP and inorganic active fillers are studied. The modified active fillers of Li 7- x -3 y Al y La 3 Zr 2- x Ta x O 12 are obtained by co-element doping with Al and Ta when LLZO is synthesized by calcination. And an high room temperature ionic conductivity of 5.357 × 10 -4 S cm -1 is exhibited by ATLLZO ceramic sheet. The composite solid electrolyte PVDF-HFP/LiTFSI/ATLLZO (PHL-ATLLZO) is prepared by solution casting method, and its electrochemical properties are investigated. The results show that when the contents of lithium salt LiTFSI and active filler ATLLZO are controlled at 40 wt% and 10%, respectively, the ionic conductivity of the resulting composite solid electrolyte is as high as 2.686 × 10 -4 S cm -1 at room temperature, and a wide electrochemical window of 4.75 V is exhibited. The LiFePO 4 /PHL-ATLLZO/Li all-solid-state battery assembled based on the composite solid-state electrolyte exhibits excellent cycling stability at room temperature. The cell assembled by casting the composite solid-state electrolyte on the cathode surface shows a discharge specific capacity of 134.3 mAh g -1 and 96.2% capacity retention after 100 cycles at 0.2 C. The prepared composite solid-state electrolyte demonstrates excellent electrochemical performance., (© 2023 IOP Publishing Ltd.)

(Poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methyl methacrylate)) PVDF-HFP/PMMA based gel polymer electrolyte comprising 0–7 wt.% TiO 2 nanoparticles has been synthesized. After introducing TiO 2 nanoparticles, the thermal properties of the PVDF-HFP/PMMA/TiO 2 composite polymer electrolyte (CPE) are remarkably improved: when the working temperature is up to 90 °C, the weight loss of CPE with 7% TiO 2 is only 12.8% of that without TiO 2 , suggesting much higher thermal stability; the shrinkage of the CPE at 130 °C can also obviously decrease from 23.4% down to 14.4% after introducing TiO 2 nanoparticles. In addition, the CPE exhibits much higher ionic conductivity and better electrochemical stability. Furthermore, the LiCoO 2 /Li cells with CPE exhibit good cyclic stability and C-rate performance: the capacity maintains 92.1% of the initial capacity after 50 cycles; the capacity can reach as large as ~ 80 mAhg − 1 even at 5 C. It is promising for PVDF-HFP/PMMA/TiO 2 CPE to meet the practical demands of high-performance and thermal safety for lithium ion batteries. [ABSTRACT FROM AUTHOR]

A PVDF-HFP gel electrolytes based DSSCs were fabricated successfully, where gel electrolytes with 2.5 wt.%, 5 wt.%, 10 wt.% and 15 wt.% PVDF-HFP are included, respectively. Linear sweep voltammetry (LSV), photocurrent–voltage measurements and electrochemical impedance spectra (EIS) were measured. As the results shown, the apparent diffusion coefficient (D app ) of I − and I 3 − decreased as PVDF-HFP increased. D app of I − and I 3 − are decreased from 1.87 × 10 − 6 to 0.67 × 10 − 6 cm 2 /s and 3.28 × 10 − 6 to 0.88 × 10 − 6 cm 2 /s, respectively. For the solar cell measurements, the short circuit current density (J sc ) were affected by the ion motilities, which was decreased from 11.58 mA/cm 2 to 8.17 mA/cm 2 , and the energy converting efficiency (η %) was decreased from 5.17% to 2.79%. For electrochemical impedance spectra (EIS) measurements, the ionic diffusion impedance for the redox-couple (I − /I 3 − ) in the gel electrolyte was also increased with the concentration of PVDF-HFP from 0.61 Ω to 8.17 Ω. In the Bode Plots, the electron lifetime (τ e ) of the 2.5 wt.% and 5 wt.% PVDF-HFP electrolytes was increased from 40.52 ms to 48.48 ms and 41.29 ms, respectively. However, τ e was decreased in the concentrations of 10 wt.% and 15 wt.% PVDF-HFP, due to the ion motilities that were decreased by excessing PVDF-HFP polymer. For gel electrolyte, the cell of 2.5 wt.% PVDF-HFP exhibited a better J SC of 10.89 mA/cm 2 , a higher energy conversion efficiency (η) of 4.75%, a higher fill factor (FF) of 61.26%, and a smaller R of 1.06 Ω than the 15 wt.% PVDF-HFP based cell. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) polymer electrolyte containing zirconium dioxide nanocrystals (ZrO 2 -NC) and lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) has been synthesized using the conventional solution casting method. The addition of ZrO2-NC into the polymeric substrate gave remarkable properties in terms of the electrolyte’s ionic conductivity as well as its bulk mechanical strength. The enhanced amorphicity of the polymeric substrate due to ZrO 2 and the nanofiller’s high dielectric constant make an excellent combination to increase the ionic conductivity (above 10 −4 S cm −1 ). Increasing the nanofiller content raises the ionic conductivity of the electrolyte by two orders of magnitude of which the optimum is 2.65 × 10 −4 S cm −1 at 13.04 wt% ZrO 2 -NC loading. Also, the Young’s modulus, an indicator of electrolyte’s mechanical stability, dramatically increased to 207 MPa upon loading 13.04 wt% ZrO 2 -NC. Using UV–vis spectroscopy, the electrolytes with 13.04% ZrO 2 -NC scanned from 200–800 nm wavelengths exhibited a maximum optical transmittance of 52.6% at 10 μm film thickness. The enhanced conductivity, high mechanical strength and reasonable optical transmittance shown by our composite polymer electrolyte make an excellent electrolyte for future energy saving smart windows such as electrochromic devices. [ABSTRACT FROM AUTHOR]

In this work, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([bdmim]BF 4 ) ionic liquid is introduced into poly(vinyl pyrrolidone)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVP/PVdF-HFP) blend host to prepare a gel polymer electrolyte (PVP/PVdF-HF-Mg(CF 3 SO 3 ) 2 ) system for a symmetrical solid-state electrical double layer capacitor (EDLC). Ionic liquid-incorporated gel polymer electrolyte (GPE) containing 7.5 wt.% [bdmim]BF 4 exhibits the optimum room temperature ionic conductivity of (2.92 ± 0.02) × 10 −3 S cm −1 and is electrochemically stable up to +2.4 V. The specific capacitance ( C s ) of the optimised GPE at 100 th cycle with porous carbon as electrode delivers 95, 133, 108 and 117 F g −1 at operating voltage of 0.8, 1.0, 1.6 and 2.0 V, respectively, under a constant current density of 100 mA g −1 . The solid-state displays the highest energy and power density of 14 W h kg −1 and 21 W kg −1 , respectively, at an operating potential of 1.0 V, which qualifies the GPE-IL for symmetrical solid-state EDLC application. [ABSTRACT FROM AUTHOR]

The hybrid polymer nanocomposites based on poly(vinylidene fluoride-co-hexaflouro propylene) (PVdF-HFP) as a host matrix, propylene carbonate as the plasticizer, and surface modified and unmodified TiO nanoparticles as fillers for dye-sensitized solar cell applications have been prepared using a solvent casting technique. The surface of TiO was modified using aminopropyltrimethoxysilane (APS), and its organic functional groups on TiO were confirmed by Fourier transform infrared (FTIR) spectroscopy. The PVdF-HFP membranes were characterized by FTIR, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), atomic force microscopic (AFM), and ultraviolet-visible (UV-Vis) spectroscopic techniques. It was found a new interaction of APS molecules on TiO surface with matrix as well as electrolyte salt. The experimental observations indicated a noticeable improvement in ionic conductivity of modified TiO of about 6.7 × 10 S/cm when compared with unmodified counterpart (TiO) as the filler within PVDF-HFP matrix. The solid state dye-sensitized solar cell has been fabricated by using silane-modified TiO/PVdF-HFP nanocomposite electrolyte and eosin-Y as sensitizer, and its photoconversion efficiency is measured about 1.47 %. [ABSTRACT FROM AUTHOR]

The effects of some important factors in the initial crystallization process of the solution casting method on the piezoelectricity of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films were extensively explored. The experimental results revealed that there is an optimal initial crystallization temperature at around 90°C. The slow cooling speed can moderately enhance the degree of crystallinity. The most important finding was that a bilayer crystalline structure caused by an asymmetrical heating pattern can enhance the formation of packed micro-fibrillar morphologies after drawing. These three points can increase the piezoelectricity of the PVDF-HFP films, indicating the increase of the extended-chain crystals ( β-phase). [ABSTRACT FROM AUTHOR]

This research concerns the development of a composite gel polymer electrolyte based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers. The nanofibers containing La2O3nanofiller were fabricated via an electrospinning process. The aim of this work was to investigate the effects of elctrospining conditions and nanofiller content on morphology and electrolyte properties of the materials. After adding La2O3nanoparticles into the polymer solution, percentage crystallinity values of the electrospun composite decreased. The addition of La2O3also resulted in an increase in ion conductivity values of the composite gel polymer electrolyte. The maximum conductivity value of the electrolyte obtained in this study was 1.43 × 10−3S/cm. [ABSTRACT FROM AUTHOR]

• Conversion of vibration energy into hydrogen energy. • The best hydrogen production is due to the higher content of β-phase PVDF. • Organic polymers are easy to deform and produce better piezoelectric catalysis. The hydrogen producing performances of metal-free organic polymers PVDF and PVDF-HFP from water splitting were investigated. The 200-min hydrogen yields of PVDF and PVDF-HFP under ultrasonic vibration are up to 355.10 and 724.64 μmol/g respectively. Because of the strong deformability and ductility, PVDF and PVDF-HFP under ultrasonic vibration were more prone to deformation, promoting their polarization to form positive and negative charges, which interacted with hydrogen ions in water to form hydrogen. The PVDF-HFP contains more β phase and less α phase and thereby shows better piezoelectric catalytic performance. Because of high hydrogen producing stability, both PVDF and PVDF-HFP are highly potential in clean energy production and wastewater treatment. [ABSTRACT FROM AUTHOR]

Surface treatment of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) fibers was conducted with coupling agents such as epoxy silane, amino silane, and titanate to improve the adhesion characteristics of PVDF-HFP fibers and polydimethylsiloxane (PDMS). The adhesion strength was largest when 4 wt% amino silane was used for surface treatment, showing a 250% improvement compared to the untreated case. Surface roughening and shrinking of the PVDF-HFP fibers were observed after surface treatment, but no chemical bonding occurred between the PVDF-HFP fibers and the coupling agents. It was thus concluded that the improvement of the adhesion characteristics of the PVDF-HFP fibers and PDMS was caused by the physical bonding between them due to the surface treatment with coupling agents. In addition, for the surface roughening mechanism, amino silane infiltration into the PVDF-HFP fibers during the surface treatment, followed by extraction during the drying process, was suggested. [ABSTRACT FROM AUTHOR]

Polymer films and membranes of poly(vinylidene fluoride co-hexafluoropropylene), PVDF-HFP, have been prepared by thermally induced phase separation (TIPS), allowing the tuning of microstructure and morphology. The obtained microstructure is explained by the Flory-Huggins theory, depending on polymer concentration and solvent evaporation temperature. The formation of a porous membrane is attributed to a spinodal decomposition of the liquid-liquid phase separation. The effect of the processing conditions on the morphology, degree of porosity, degree of crystallinity and crystalline polymorph, thermal, dielectric and piezoelectric properties of the PVDF-HFP polymer were evaluated. The crystalline phase and degree of crystallinity depend on the processing conditions and further influence the dielectric and piezoelectric response. The piezoelectric coefficient is correlated with the β-phase content and decreases with decreasing polymer concentration in the initial solution at a given evaporation temperature. [ABSTRACT FROM AUTHOR]

Abstract: In this work, 1–butyl–3–methyl imidazolium trifluoromethanesulfonate (BMITf) is employed as ionic liquid in polymer blend electrolyte system based on poly(ethyl methacrylate) (PEMA) and poly(vinylidenefluoride–co–hexafluoropropylene) (PVdF–HFP) in the weight ratio of 70 to 30. The films were prepared by solution casting. Lithium trifluoromethanesulfonate (LiTf) is the lithium ion (Li+) provider. Addition of BMITf into the optimized PEMA/PVdF–HFP–LiTf composition increased the ionic conductivity of the system. The highest room temperature ionic conductivity of 8.59×10−5 S cm−1 was exhibited by PEMA/PVdF–HFP–LiTf containing 60wt.% BMITf. Vibrational studies by FTIR show that the imidazolium cation (BMI+) interacts with the oxygen atoms in C=O and C–O–C groups of PEMA, and also fluorine atoms in CF2 groups of PVdF–HFP. Addition of BMITf into the PEMA/PVdF–HFP–LiTf system increases the amount of free ions leading to improvement in the ionic conductivity. The thermal stability of the polymer electrolytes is improved to above 275°C by the addition of BMITf. [Copyright &y& Elsevier]

Abstract: Gel type polymer electrolytes with PVDF-HFP as polymer host, NaI salt and EC/PC as plasticizers have been prepared and optimized for use in a dye sensitized solar cell (DSSC). The polymer electrolyte containing 48wt. % (PVDF-HFP)–32wt. % NaI–20wt. % (EC/PC) exhibits the highest room temperature conductivity of 1.53×10−4 S cm−1. This electrolyte has been used in the fabrication of a DSSC with the configuration FTO/TiO2/natural dye/electrolyte/Pt/FTO. The natural dyes used anthocyanin and chlorophyll were solvent extracted from black-rice and pandanus amaryllifolius leaves respectively. UV-vis absorption spectra of anthocyanin, chlorophyll and the mixture of anthocyanin and chlorophyll in the volume ratio 1:1 were recorded. The anthocyanin shows an absorption peak at 532nm. In the same region chlorophyll absorption shows a peak at 536nm and also has a prominant peak at 665nm. On mixing anthocyanin and chlorophyll two prominant peaks are observed at 536 and 665nm. The DSSC containing the dye mixture exhibits the best performance with a short-circuit current density of 2.63mAcm−2, open-circuit voltage of 0.47V, fill factor of 0.58 and the highest photo-conversion efficiency of 0.72% under the illumination of 100mW cm−2 white light. Under illumination of lower light intensity of 60mW cm−2 and 30mW cm−2, the fill factor enhanced from 0.58 to 0.59 and 0.60 and the photo-conversion efficiency increased from 0.72% to 1.11% and 1.85% respectively. [Copyright &y& Elsevier]

Growing environmental concerns are stimulating researchers to develop more and more efficient materials for environmental remediation. Among them, polymer-based hierarchical structures, attained by properly combining certain starting components and processing techniques, represent an emerging trend in materials science and technology. In this work, graphene oxide (GO) and/or carbon nanotubes (CNTs) were integrated at different loading levels into poly (vinyl fluoride-co-hexafluoropropylene) (PVDF-co-HFP) and then electrospun to construct mats capable of treating water that is contaminated by methylene blue (MB). The materials, fully characterized from a morphological, physicochemical, and mechanical point of view, were proved to serve as membranes for vacuum-assisted dead-end membrane processes, relying on the synergy of two mechanisms, namely, pore sieving and adsorption. In particular, the nanocomposites containing 2 wt % of GO and CNTs gave the best performance, showing high flux (800 L × m -2 h -1 ) and excellent rejection (99%) and flux recovery ratios (93.3%), along with antifouling properties (irreversible and reversible fouling below 6% and 25%, respectively), and reusability. These outstanding outcomes were ascribed to the particular microstructure employed, which endowed polymeric membranes with high roughness, wettability, and mechanical robustness, these capabilities being imparted by the peculiar self-assembled network of GO and CNTs.

Here, we report the fabrication of nanocomposite comprising of CuO and poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) for application in flexible piezoelectric nanogenerators (PENG). The chemically grown CuO nanostructures have been characterized through electron microscopy, x-ray diffraction, and spectroscopic techniques. It has been found that the incorporation of optimal CuO nanostructures in PVDF-HFP can increase the output voltage of the PENG by 22 times and is assigned to the increment in the effective dielectric constant of host PVDF-HFP. Further, the nanogenerator exhibits a maximum power of ∼20 μ W cm -2 at 3 MΩ load and can charge a capacitor under continuous bio-mechanical impart. Further, upon slight alteration of the device configuration, the output of the nanocomposite-based nanogenerator can be enhanced under illumination condition. The increment in overall piezopotential through photoexcitation in optically active CuO nanostructures can be assigned to the increment in output voltage. The wavelength dependent output variation reveal the maximum output of the PENG under blue light. Further, under white light illumination, the nanogenerator exhibits a maximum power which is 3 times higher than in dark condition and can charge a capacitor 52 times faster. The development of such superior flexible and optically active nanogenerators are quite promising for futuristic self-powered devices operated under mechanical and solar energies., (© 2022 IOP Publishing Ltd.)

Aqueous rechargeable zinc-based batteries have recently gained tremendous attention because of their low cost and high safety. However, the issues associated with the zinc metal anode, including corrosion, H 2 evolution, and dendrite growth, hinder their practical applications. Herein, we design a hybrid organic/inorganic interphase composed of poly(vinylidene fluoride-co-hexafluoropropylene), silica, and zinc triflate to stabilize the zinc metal anode in a mild aqueous electrolyte. It is proven that the artificial interphase reduces corrosion of the Zn metal in the ZnSO 4 electrolyte and suppresses dendrite growth by regulating Zn 2+ deposition. Therefore, the lifespan of symmetrical cells with coated Zn could be enhanced to over 960 h with a stripping/plating capacity of 0.5 mAh cm -2 . In addition, zinc-ion batteries including a sodium vanadate cathode and a coated Zn anode could achieve 3000 cycles with nearly no capacity fading at 5 A g -1 .

Lithium metal batteries hold great promise for high-energy-density rechargeable battery systems. However, Li metal anode suffer from poor stability and safety hazards in liquid electrolytes due to uncontrollable Li dendrites growth and unstable solid-electrolyte interphase (SEI). Herein, this work constructs a porous PVDF-HFP layer (PPHL) with high polarity as interfacial layer for dendrite-free and stable Li metal anodes in both ether and carbonate electrolytes. PPHL can not only physically suppress the Li dendrites owing to high mechanical strength, but also regulate the even Li-ion flux due to porous and highly polar β phase structure. "LiF-rich" SEI induced by PPHL is found responsible to enhance the stability of SEI and improve Li-ion diffusion for stable Li plating/stripping behaviors. Therefore, Li metal with PPHL shows uniform and dense Li deposition without Li dendrites. Li/Li symmetric cells exhibit high stability and reversibility in ether electrolyte for 1400 h and carbonate electrolyte for 600 h with high Li-ion transference number. Li//LFP full battery shows excellent cyclic stability and rate performance with high capacity retention in commercial carbonate electrolyte. PVDF-HFP layer with high porosity and polarity is investigated for stable Li metal anodes, which can induce "LiF-rich" SEI to enhance the stability of interface and redistribute Li-ion flux with uniform Li+ transport. Thus, Li metal anodes show uniform Li deposition and less volume change, and exhibit high stability and reversibility in both ether and carbonate electrolytes. [Display omitted] • PPHL shows high porosity and polarity due to the porous structure and polar functional groups of β phase, which can redistribute Li-ion flux with uniform and fast Li+ transport. • PPHL can induce "LiF-rich" SEI to enhance the stability of SEI and enable homogeneous Li-ion flux. • With the protection of PPHL, Li metal anode exhibits smooth and uniform Li deposition without Li dendrites, and keeps stable and dense structure even after 100 cycles. • Li/Li symmetric cells exhibit high stability and reversibility in ether electrolyte for 1400 h and carbonate electrolyte for 600 h. • Li//LFP full battery displays impressive cyclability for 500 cycles with almost no capacity fading at 1C in commercial carbonate electrolyte. [ABSTRACT FROM AUTHOR]

The Al2O3/PVDF-HFP separator membranes are prepared by phase transformation with poly (vi-nylidene fluoride-hexafluoropropylene) as the matrix. Then their properties including liquid electrolyte uptake ratio, heat resistance, morphology and crystal structure are tested and compared with that of PVDF-HFP and a commercialized separator. The results show that the Al2O3/PVDF-HFP separators have a high uptake ratio of 16. 8% μm, an ionic conductivity of 0. 32mS·cm-1, an ionic transference number of 0. 91 and an electrochemical stability window of 5.2 V. The assembled battery with Al2O3/PVDF-HFP separator exhibits excellent cycle and rate performances, indicating the separator has a great potential as a new generation separator for power battery. [ABSTRACT FROM AUTHOR]

A polymer electrolyte based on the blending of poly(vinylidene fluoride-hexafluoropylene) (PVDF-HFP) and hydroxypropyl methyl cellulose (HPMC) was prepared for the first time. The structure and performance of the gel polymer electrolyte were characterized and measured by X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, electrochemical impedance spectroscopy, linear sweep voltammetry, and by a charge/discharge test. The results show that the gel polymer electrolyte has the best performance when PVDF-HFP/HPMC ratio ( w/ w) is 4:1. At room temperature, the ionic conductivity can reach 0.38 × 10 S cm, the electrochemical stable window is up to 5.0 V (vs. Li/Li), and the half cell of Li/GPE/LiMnO shows high-discharge-specific capacity and good cycling performance. [ABSTRACT FROM AUTHOR]

Carbon nanofiber (CNF)/polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) composite film was prepared by solution casting and melt pressing. The resultant 2 % CNF/PVDF-HFP composite films were uniaxially drawn at 50 °C, 75 °C, and 100 °C, respectively. In the SEM images, the morphology of drawn CNF/PVDF-HFP composite film confirmed the orientation of the CNF and the polymer matrix. The WAXD results showed the coexistence crystal phase of PVDF-HFP. The drawn CNF/PVDF-HFP composite film demonstrates improved electrical properties. The DSC thermogram results indicated no change in the melting temperature but slightly increased crystallinity with increasing drawing temperature. Dynamic mechanical analysis and tensile test showed an improvement in the storage modulus and stress at a drawing temperature of 75 °C. [ABSTRACT FROM AUTHOR]

Abstract: Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membranes were prepared via the electrospinning method. Three sets of mats, with different fiber diameters and physical properties, were obtained by varying polymer concentration from 10 to 15wt%. Membranes were formed by hot pressing the prepared mats to fuse the fibers. As prepared mats were hot pressed in order to control the membranes dimensional stability and mechanical strength and to alter the pore size and pore size distribution. The effects of hot pressing and variation of fiber diameter on pore size distribution, porosity, contact angle, gas permeation, and liquid water entry pressure (LEP) of the fabricated membranes were all studied. Optimized membranes were obtained with mean pore size, porosity, contact angle and LEP of 0.26μm, 58±5%, 125°±2.41 and 19.1psi, respectively. Fabricated membranes were tested for desalination by direct contact membrane distillation and a water flux value of 20–22Lh−1 m−2 was obtained with a salt rejection (SR) ratio of 98%. [Copyright &y& Elsevier]

Abstract: Core–shell structural single ionic conductor SiO2@Li+ was successfully synthesized from vinyltriethoxysilane, sodium p-styrenesulfonate and LiOH·H2O by hydrolysis, polymerization and ion exchange and confirmed by TEM and FT-IR. The poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP)-based composite polymer electrolyte (CPE) membrane doped with SiO2@Li+ was prepared by phase inversion method and the desirable CPE was obtained after being activated in liquid electrolyte. The physicochemical properties of the CPE were characterized by SEM, XRD, TG, and electrochemical measurements. The results show that the CPE membrane presents uniform surface with abundant interconnected micro-pores and possesses excellent mechanical performance with high decomposition temperature about 450°C; and adding SiO2@Li+ into matrix remarkably decreases the crystallinity but enhances ionic conductivity of the CPE membrane; the ionic conductivity and lithium ion transference number at room temperature are up to 3.885mScm−1 and 0.4374, respectively, and the reciprocal temperature dependence of ionic conductivity of as-prepared CPEs follows Vogel–Tamman–Fulcher relation. The battery properties of the assembled cells using CPE doped with SiO2@Li+ as electrolyte show excellent rate and cycle performance, which is partly attributed to the improved interfacial performance between the electrolyte and electrodes and partly to enhanced electrochemical working window and lithium ion transference number. [Copyright &y& Elsevier]

To improve the distribution properties of nanoparticles in the polymer electrolyte, micro-porous polymer electrolyte PVDF-HFP-SiO2 (OP-10) was prepared with phase inversion method by adopting nano-sized SiO2 as the inorganic filler and OP-10 as dispersant. The morphology, crystal structure and electrochemical properties of the electrolyte were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), electrochemical impedance spectra (EIS). The results showed that the addition of nano-SiO2 suppressed the crystallinity of polymer electrolyte and enhanced the tensile intensity. The ionic conductivity was improved, the highest ionic conductivity (20 °C) of the PVDF-HFP-SiO2 (OP-10) polymer electrolyte was 4.90 x 10-3S ⋅ cm-1, with a high electrochemical stability window of 5.3 V, and the corresponding cation transference number was 0.83. The distribution of SiO2 and interracial compatibility of nanometer particles were improved by the addition of OP-10. [ABSTRACT FROM AUTHOR]

The aging towards the ionic conductivity have been studied using of different lithium salts namely, lithium bis(oxalate)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium fluoroalkylphosphate (LiFAP) and LiPF in polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) matrix. The crystallization behavior of LiBOB and LiDFOB has been noticed for the first time during storage of such membranes within the texture of PVdF-HFP matrix. At the same time, such behavior has not been observed in the case of LiFAP and LiPF based membranes. The growth of such crystallites would certainly hinder the mobility mechanism of Li ions and it has been confirmed by ionic conductivity measurements. The formation of such crystals has been validated through scanning electron microscopic studies. [ABSTRACT FROM AUTHOR]

Abstract: Polymer electrolyte composites (PECs) based on poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) that contained lithium perchlorate (LiClO4) were prepared. N-doped TiO2 (N-Ti) was used as a filler to enhance the Li+ ion conductivity. Structural modification and electrochemical properties of the PECs were investigated in order to understand the effect of N–Ti in the polymer matrix on ionic conductivity. The PECs prepared with different N–Ti contents were characterized by SEM, mapping, DSC, and a.c. impedance. From the results, the prepared N–Ti-filled PECs showed a good ability to absorb and retain the Li+ ion. The presence of N–Ti in PVDF-HFP was resulted in increasing the ion conductivity significantly. The highest ion conductivity (6.7×10−4 S/cm) was observed at a relative low N–Ti content (2.5wt.%). It is believed that the addition of N–Ti could provide the foundation for the ionic transportation and ion-mobility of the PECs and the N-doping on TiO2 led to a more enhanced ionic conductivity by higher interaction between polar groups, such as O and N of N–Ti and Li+ ions. [Copyright &y& Elsevier]

Abstract: Poly(ethyl methacrylate), PEMA and poly(vinylidenefluoride-co-hexafluoropropylene), PVdF-HFP have been blended in the weight ratio 70:30. The blend has been incorporated with lithium trifluoromethanesulfonate (LiCF3SO3) and added with ethylene carbonate (EC) and propylene carbonate (PC). The sample 70wt.% PEMA/PVdF-HFP – 30wt.% LiCF3SO3 exhibits the highest room temperature ionic conductivity of 2.87×10−7 S cm−1 for the blend-salt system. The sample in the PC system (designated 6PC) has the highest room temperature conductivity of 1.46×10−6 S cm−1. The highest conducting EC system has conductivity of 1.05×10−4 S cm−1 and the sample is designated as 6EC. The polymeric gel electrolytes are transparent and mechanically stable at room temperature. An electrochromic device (ECD) with configuration glass/FTO/WO3/sample/CeO2-TiO2/FTO/glass utilizing S30, 6PC and 6EC as electrolytes have been fabricated. The cyclic voltammogram (CV) of glass/FTO/WO3/6EC/CeO2-TiO2/FTO/glass shows a cathodic peak occurring at −1.3V upon coloration while an anodic peak is observed at −0.8V during bleaching process. [Copyright &y& Elsevier]

Abstract: Poly(ethyl methacrylate), PEMA and poly(vinylidenefluoride-co-hexafluoropropylene), PVdF-HFP have been chosen as hosts for the development of a polymer blend electrolyte system. Lithium trifluoromethanesulfonate (triflate), LiCF3SO3 is the lithium ion, Li+ provider. The ratio of PEMA:PVdF-HFP in the blend is fixed at 70:30 in order to obtain transparent films with good mechanical stability. The polymers and LiCF3SO3 salt have been refluxed for 2h at temperatures between 55 and 65°C. The concentration of LiCF3SO3 salt has been varied from 0 to 40wt.%. Fourier transform infrared (FTIR) spectroscopy has shown that blending between PEMA and PVdF-HFP has occurred from the changes in the CH2 scissoring [δ(CH2)], asymmetrical O–C2H5 bending [γ(OC2H5)], CH2 twisting [τ(CH2)], C–O stretching of –COO– group [ν(CO)], asymmetrical C–O–C stretching [ν a(COC)] and C–O stretching of –OC2H5 [ν(C–O)] from PEMA as well as the symmetrical CF2 stretching [ν s(CF2)], α-phase and the amorphous region of PVdF-HFP. Complexation occurs via the coordination of Li+ ions with the oxygen atom in the carbonyl (Cter (–COC–) groups of PEMA as well as with the fluorine atom in –CF2 and –CF3 groups in PVdF-HFP. Curve fitting of spectral bands in the symmetrical ν s(SO3) stretching region in the polymer blend–salt complexes has shown that free ions (1031–1032cm−1) and ion pairs (1040–1042cm−1) are present in samples incorporated with 10wt.% LiCF3SO3 and above, while ion aggregates at 1049cm−1 are formed when 40wt.% LiCF3SO3 is added into the polymer blend. The increase in the ionic conductivity at high salt contents could be explained by the greater amount of free ions as compared to ion pairs and ion aggregates. [Copyright &y& Elsevier]

Abstract: Macroporous polymer separators based on poly(vinylidene fluoride) (PVdF) and several VdF copolymers were prepared by a phase inversion process using acetone as a solvent. The resulting macroporous separators were characterized in terms of morphology, swelling behaviour, thermal and mechanical properties and ionic conductivity. The PVdF separator had a highly porous structure (80%) and exhibited good mechanical properties. Once filled by a molar solution of tetraethylammonium tetrafluoroborate (TEABF4) in acetonitrile (AN) it provided enhanced conductivity (18mScm−1 at 25°C) compared with commercial cellulose and Celgard™ separators. [Copyright &y& Elsevier]

Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) films were prepared using either a melt pressing or solution casting methods. The resulting PVDF-HFP films were drawn uniaxially at various drawing temperatures and speeds. The mp-PVDF-HFP films were more transparent and had more drawability than the sc-PVDF-HFP films. The crystal form of the initial films was the alpha-phase (non polarity) of PVDF. The maximum draw ratio was 7.6. The mp-PVDF-HFP films were prepared at a drawing speed of 2500 %/min at 100 °C. With increasing drawing speed, the beta-phase (polarity) became the dominant phase of PVDF in mp-PVDF-HFP films. The thermal properties of the resulting PVDF-HFP films improved with increasing drawing temperature. [ABSTRACT FROM AUTHOR]

Abstract: The effects of incorporation of aluminum nitride (AlN) in the gel polymer electrolyte (GPE) of a quasi-solid-state dye-sensitized solar cell (DSSC) were studied in terms of performance of the cell. The electrolyte, consisting of lithium iodide (LiI), iodine (I2), and 4-tert-butylpyridine (TBP) in 3-methoxypropionitrile (MPN), was solidified with poly(vinyidene fluoride-co-hexafluoro propylene) (PVDF-HFP). The 0.05, 0.1, 0.3, and 0.5wt% of AlN were added to the electrolyte for this study. XRD analysis showed a reduction of crystallinity in the polymer PVDF-HFP for all the additions of AlN. The DSSC fabricated with a GPE containing 0.1wt% AlN showed a short-circuit current density (J SC) and power-conversion efficiency (η) of 12.92±0.54mA/cm2 and 5.27±0.23%, respectively, at 100mW/cm2 illumination, in contrast to the corresponding values of 11.52±0.21mA/cm2 and 4.75±0.08% for a cell without AlN. The increases both in J SC and in η of the promoted DSSC are attributed to the higher apparent diffusion coefficient of I− in its electrolyte (3.52×10−6 cm2/s), compared to that in the electrolyte without AlN of a DSSC (2.97×10−6 cm2/s). At-rest stability of the quasi-solid-state DSSC with 0.1wt% of AlN was found to decrease hardly by 5% and 7% at room temperature and at 40°C, respectively, after 1000h duration. The DSSC with a liquid electrolyte showed a decrease of about 40% at room temperature, while it virtually lost its performance in about 150h at 40°C. Explanations are further substantiated by means of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and by porosity measurements. [Copyright &y& Elsevier]

Abstract: Polymeric catalytic membrane reactors offer a larger flexibility over conventional reactors. The most-used method to generate polymer-based catalytic membranes is the phase inversion that, however, presents some limitations; in particular, the difficulty in generating a uniform distribution of the loaded materials. In this work, we use two new processes for the formation of membranes loaded with catalyst for potential applications in catalysis: supercritical assisted phase inversion and supercritical assisted gel drying, applied to formation of poly(vinylidene fluoride-co-hexafluoropropylene) membranes loaded with palladium nanoparticles. We analyzed the effect of process parameters (polymer concentration, catalyst concentration, pressure, temperature) on the membranes morphology. The supercritical phase inversion process produced cellular asymmetric structures with cell size ranging between 3 and 6μm and nanoporous homogeneous networks, depending on the process conditions. Palladium nanoparticles homogeneous distributions were obtained only operating at selected process conditions, i.e., pressures larger than 150bar and temperatures lower than 45°C. Supercritical gel drying allowed homogeneous nanoporous membranes formation at all the tested process conditions: they were characterized by very high porosity (higher than 90%) and a very uniform catalyst distribution. [Copyright &y& Elsevier]

Abstract: Nanocomposite polymer electrolyte membranes were prepared by phase inversion technique in polyvinylidenefluoride–hexafluoropropylene (PVdF–HFP) matrix. These membranes were gelled with 0.5M LiBOB in EC:DEC (1:1 v/v). These gel polymer membranes (GPMs) were incorporated with nanoparticles of AlO(OH) n and prepared composite polymer membranes (CPMs) also. The a.c. impedance analysis shows that AlO(OH) n filled membrane exhibits conductivity of 1.82×10−3 Scm−1 at ambient temperature. The Li/CPM/LiFePO4 cell delivered a specific discharge capacity of 158 and 147mAhg−1 at first and at 20th cycle respectively discharged at C/20 rate. The cell experiences a capacity fade of 0.1mAhg−1 cycle−1 over the investigated 20 cycles. The studies vindicate that AlO(OH) n filled PVdF–HFP polymer membranes could be the potential material to use as separator cum electrolyte in lithium batteries in conjunction with LiFePO4 as a counterpart. [Copyright &y& Elsevier]

One of the alternatives proposed to obtain controlled release pharmaceutical formulations is the generation of membranes loaded with an active principle; until now, several methods have been proposed, but all these techniques present various limitations. The production of loaded membranes based on aerogels has also been tested, but several problems are still open due to the possible drug stratification and to the collapse of the porous structure during the drying process. In this work, we tested a supercritical CO2 (SC-CO2) drying process for the formation of PVDF-HFP loaded aerogels. We performed experiments at pressures ranging between 150 and 250 bar and at temperatures ranging between 35 and 55°C. We selected the PVDF-HFP-acetone-ethanol solution at 15% w/w polymer and modified the drug (amoxicillin) concentration from 20 to 30% w/w with respect to PVDF-HFP as the base case. The SC-CO2 drying process was confirmed to be a valid alternative to generate loaded structures; indeed, aerogels characterized by nanometric networks (mean pores diameter of about 300 nm) with homogeneous drug distribution were obtained. Drug controlled release experiments were also performed and a quasi-zero order release kinetic was observed. [ABSTRACT FROM AUTHOR]

Abstract: Polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) has received much attention recently as a promising membrane material for membrane contactor application. A systematic study has been carried out to investigate the effects of polyethylene glycol (PEG) with different molecular weights and different loadings as an additive on the fabrication of PVDF-HFP asymmetric microporous hollow fiber membranes. Moreover, the synergetic effects of coagulation temperature and the second additive (lithium chloride: LiCl) with PEG are also evaluated. Experiments revealed that the addition of PEG into the PVDF-HFP/NMP solution resulted in the system thermodynamically less stable in reaction with water, promoting rapid phase demixing in the phase inversion process. When the same 3wt% PEG was added into the dope solution, the dimension of finger-like macrovoids of the resultant membrane increased in parallel with the increase of PEG molecular weight from 200 to 600 and 6000kDa, and pure water permeability (PWP) also increased accordingly. An increase in PWP was also observed when PEG-200 loading in the dope solution was increased from 3 to 5 and 10wt%, corresponding to the morphology change of resultant membranes. As a synergetic effect of coagulation temperature with PEG, the finger-like pores occurred in the membrane at room temperature expanded to much larger macrovoids using 10°C water as the coagulant, and the big finger-like pores almost disappeared when the coagulation bath temperature was increased to 40°C because of delayed phase demixing. The big macrovoid size can also be suppressed by adding the second small molecule additive, LiCl, due to its strong interactions with NMP and PVDF-HFP to delay the dope precipitation. The irregular inner contour of the membrane can be eliminated by the increase of coagulation bath temperature to 40°C. The hollow fiber membrane made by a dope of PVDF-HFP/PEG-6000/LiCl/NMP (15/3/3/79 in weight) using 40°C water as the coagulant exhibited a high PWP of 117L/m2 hatm and reasonably good MWCO of 150kDa. An improvement has been made in the current work as compared to previous PVDF-HFP hollow fiber membranes reported in literatures. [Copyright &y& Elsevier]

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes used as the matrix for the gel electrolyte for a lithium battery were prepared via the thermally induced phase separation (TIPS) process using a diluent mixture of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP). With the assistance of the phase diagram, the membrane microstructure was controlled by only varying the DBP/DEHP ratio in the diluent mixture. The mechanism for the formation of different membrane microstructures was proposed. The effects of membrane microstructure on the membrane performance and the electrochemical properties of the resulting gel electrolyte were also investigated. In addition, a cycle test of a lithium-ion cell with the gel electrolyte based on the membrane prepared via liquid–liquid phase separation showed stable cycling capacity, thus presenting great promise for the use of this membrane as the gel electrolyte matrix for lithium batteries. [ABSTRACT FROM AUTHOR]