VDF HFP Research Articles

Magnetic field assisted high performance triboelectric nanogenerators based on P(VDF–HFP)/NiFe2O4 nanofiber composite

Triboelectric nanogenerators (TENGs), which are powered by Maxwell's displacement current, have a wide range of applications, including energy harvesting and self-powered sensors. However, very little attention has been paid to the effect of the ferromagnetic medium on TENG displacement current. Herein, flexible ferrimagnetic poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF–HFP))/nickel ferrite (NiFe2O4) fiber composite film based TENGs were fabricated and their performances were analysed. Highly crystalline, ferrimagnetic NiFe2O4 nanofibers with high aspect ratio were prepared using electrospinning technique by systematic optimization of spinning parameters. Thereafter, the fibers were reinforced into the polymeric matrix to improve the β–phase and dielectric constant which in turn significantly enhanced the TENG performance. The β–phase enhancement in the composite films was confirmed by XRD and FTIR analysis; 77 % of the β–phase was achieved with the incorporation of NiFe2O4 fiber. Morphological features were examined using SEM and AFM, which revealed more β–phase spherulite formation in the composite films. A notable increase in the dielectric properties was evidenced with the addition of NiFe2O4 fibers and a maximum dielectric constant of∼26 was attained at 100 Hz. The TENG was developed using P(VDF-HFP)/NiFe2O4 and nylon which generated an output voltage (Vpp) and current (Ipp) values of 584 V and 25 μA, respectively. Furthermore, the performance of TENG under an external magnetic field was examined, and a notable improvement in performance was observed, paving the way for the application of NiFe2O4 fibers in hybrid energy harvesters and self-powered sensors.

Effect of Inorganic Nanoparticles on Energy‐Storage Properties of P(VDF–HFP)‐Based Nanocomposites

Polyvinylidene fluoride (PVDF) and its copolymers have been widely used in polymer‐based film capacitors due to their relatively high permittivity and electrical displacement compared with other polymers. Herein, poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF–HFP)) is selected as the polymer matrix, and 0.5 (Bi0.5Na0.5)TiO3–0.5(Sr0.85Sm0.1)TiO3 (BNT–SST) nanoparticles are added as the filler into the polymer to prepare BNT–SST/P(VDF–HFP) nanocomposites. The microstructure, electrical properties, mechanical properties, and energy‐storage properties of the nanocomposites are investigated. The addition of BNT–SST nanoparticles improves the dielectric characteristics and breakdown strength of the nanocomposites. Particularly, when the BNT–SST filler content is 0.7 vol%, the highest breakdown strength reaches 545 MV m−1, which is 1.3 times higher than pure P(VDF–HFP). In addition, the insulation and mechanical properties of BNT–SST/P(VDF–HFP) composite films are improved. The highest direct current resistivity and Young's modulus obtained by 0.7 vol% BNT–SST/P(VDF–HFP) nanocomposites are 6.8 × 1013 Ω cm and 1.94 GPa, respectively. More importantly, at 545 MV m−1, the energy‐storage density and efficiency of 0.7 vol% BNT–SST/P(VDF–HFP) composites are 19.07 J cm−2 and 67.01%, respectively, which are better than other polymer matrix composites. These findings suggest that the addition of inorganic nanoparticles has important research implications for improving the energy‐storage performance of polymer‐based film capacitors.

Energy storage properties of flexible dielectric composites containing Ba0.4Sr0.6TiO3/MnO2 heterostructures

Although flexible dielectric composites are attractive for high-power energy storage, their low energy storage density (Ue) and efficiency (η) significantly restrict their practical applications. Ue is difficult to further improve due to the limitation of theoretical dielectric constant and polarization of the polymer matrix and filler. Herein, an effective strategy to enhance the Ue and η of dielectric polymers by constructing Ba0.4Sr0.6TiO3/MnO2 (BST/MnO2) heterostructure as filler in BST/MnO2/P(VDF–HFP)&PMMA composites is proposed. On one hand, the tightly attached MnO2 on BST particles can improve the local electric field intensity on the BST, enhancing the Ti4+ ionic displacement and contributing to the high polarization. On the other hand, semiconductive MnO2 with higher electron affinity can trap the injected and excited electrons, and the large trap energy level between MnO2 and the polymer that could inhibit the mobility of free charge carriers in the film. Thus, the leakage current density is suppressed and the breakdown strength is enhanced. Both of them improve the energy storage performance of film, resulting in the excellent Ue of 21.2 J cm−3 and high η of 75.4 % at 667 kV mm−1. The proposed heterostructure strategy offers a new paradigm for improving the energy storage performance of composite capacitors.

Novel inorganic fillers of 1D hydroxyapatite nanowires induced superior energy storage performances of P(VDF–HFP)-based composite films

Newly one-dimensional hydroxyapatite nanowires are synthesized and applied in P(VDF–HFP) nanocomposites for energy storage application. Excellent Ud of ∼27.6 J cm−3 accompanied with high η of ∼72.9% at Eb of 650 MV m−1 are achieved.

Electrochromism of Viologen/Polymer Composite: From Gel to Insulating Bulk for High-Voltage Applications.

Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of great demand in the power industry. Typical electrochromic phenomenon is based on redox of the material, triggered by a voltage smaller than 5 V with a continuous current in μA~mA level, which is not applicable to high electric fields above 106 V/m with pA~nA operation current in power equipment. Until now, no naked-eye observation technique has been realized for space charge detection to ensure the operation of power systems as well as the safety of maintenance workers. In this work, a viologen/poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF–HFP)) composite is investigated from gel to insulating bulk configurations to achieve high-voltage electrical-insulating electrochromism. The results show that viologen/P(VDF–HFP) composite bulk can withstand high electric fields at the 107 V/m level, and its electrochromism is triggered by space charges. This electrochromism phenomenon can be visually extended by increasing viologen content towards 5 wt.% and shows a positive response to voltage amplitude and application duration. As viologen/P(VDF–HFP) composite bulk exhibits a typical electrical insulating performance, it could be attached to the surface of insulating structures or clamped between metal and insulating materials as a space charge accumulation indicator in high-voltage power equipment.

Simultaneous Realization of Significantly Enhanced Breakdown Strength and Moderately Enhanced Permittivity in Layered PMMA/P(VDF–HFP) Nanocomposites via Inserting an Al2O3/P(VDF–HFP) Layer

Simultaneous Realization of Significantly Enhanced Breakdown Strength and Moderately Enhanced Permittivity in Layered PMMA/P(VDF–HFP) Nanocomposites via Inserting an Al₂O₃/P(VDF–HFP) Layer

Influence of pore morphologies on the mechanical and tribo-electrical performance of polydimethylsiloxane sponge fabricated via commercial seasoning templates

This work demonstrated the influence of pore morphologies on the mechanical behavior and tribo-electrical performance of fabricated polydimethylsiloxane (PDMS) sponge. Commercial seasonings with different 3D geometric shapes were used as a sacrificial template to control the pore structure of the PDMS sponge. The result indicated that the softest PDMS sponge was molded by using a sodium chloride (NaCl) crystal template, as indicated by the lowest compressive modulus value. Then, P(VDF–HFP) was incorporated into PDMS prepolymer in order to enhance the charge generation characteristic of PDMS. Besides, the composite 3D structure was revealed using synchrotron radiation X-ray tomographic microscopy (SRXTM). Interpretation from the SRXTM result confirmed that the porous structure had different pore shapes, i.e., an octahedral-like shape and a circular-like shape in a particular sponge. By pairing the composite PDMS sponge with an aluminum (Al) plate for the triboelectric nanogenerator (TENG), the maximum electrical outputs of ~29.9 V and ~0.56 μA for voltage and current, respectively, were detected with loading 50 wt% of P(VDF – HFP). The presented TENG was applied successfully for sensing basic human activities practically, which demonstrated potential applications in wearable electronics.

Structural, Vibrational, Electrical, Electrochemical and Capacitive Investigations on Ionic Liquid Doped P (VDF-HFP) + NaSCN Based Polymer Electrolytes

Background: Solid polymer electrolyte (SPEs) films based on poly (vinylidene fluoride-co-hexafluoropropylene) P(VDF–HFP) and sodium thiocyanate (NaSCN) are prepared using the solution casting technique. Methods: Ionic liquid (IL; 1-ethyl-3-methyl-imidazolium tricyanomethanide ([EMIM] [TCM]) is incorporated into the prepared polymer-salt complex matrix to enhance its ionic conductivity further. Polarized optical microscopy (POM) shows a change in the surface morphology of IL doped polymer electrolyte films. The composite nature of polymer electrolyte films is confirmed using Fourier transform infrared (FT-IR) spectroscopy via studying ion-ion and ion-polymer interactions. The structural morphology of ionic liquid doped polymer electrolyte films (ILDPE) confirms the complexation between the ionic liquid ([EMIM][TCM]), salt (NaSCN) and polymer P(VDF-HFP). This is further confirmed using DSC and XRD measurements. The XRD structural analysis confirms that the intensity of crystalline peaks present in IL doped solid polymer electrolyte films decreases as compared to that of the pure polymer as well as polymer salt complex system. XRD clearly indicates the enhancement in its amorphous nature, which is necessary to increase the conductivity. Results: The incorporation of IL into polymer salt-complex matrix leads to changes in the melting of polymer electrolytes, confirmed by DSC thermograms. Polymer electrolyte films are also characterized using impedance spectroscopy (IS) to check their electrical properties. The highest ionic conductivity is found to be 7.80×10-4 S cm-1 for 6 wt% IL doped polymer electrolyte film. Conclusion: The Linear sweep voltammetry (LSV) analysis shows that the optimized polymer gel electrolyte is electrochemically stable up to 1.5 V. The calculated value of ionic transference number (tion) is found to be 0.985. A laboratory scale electrical double layer capacitor (EDLC) has been fabricated using this highly conducting polymer electrolyte film. The specific capacitance value is found to be 1.31 F g-1.

Robust Succinonitrile Plastic Crystal-Based Ionogel for All-Solid-State Li-Ion and Dual-Ion Batteries

We have synthesized highly conducting and electrochemically stable solidlike ionogels based on poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF–HFP) copolymer matrix, succinonitrile (SN) plas...

Layer-structured BaTiO3/P(VDF–HFP) composites with concurrently improved dielectric permittivity and breakdown strength toward capacitive energy-storage applications

Layer-structured nanocomposites with concurrently improved dielectric permittivity and breakdown strength, as well as superior energy-storage performances are obtained.

Magnetoelectric response and tunneling magnetoresistance behavior of flexible P(VDF-H FP)/Cobalt ferrite nanofiber composite films

Fabrication of magnetoelectric (ME) polymer composite films by embedding ferromagnetic cobalt ferrite (CoFe2O4) nanofibers into electroactive poly(vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) matrix is reported. Single-phase CoFe2O4 nanofibers made of cubic spinel nano crystallites are synthesized by using electro-spinning method, whereas the solution-casting technique is adapted to prepare flexible polymer composite films. The influence of CoFe2O4 nanofiber on structural, functional, magnetic, ferroelectric, and magnetoresistance properties of the composite films is investigated. The cross-coupling between ferroelectric and ferromagnetic orderings is ensured, by the variations of ferroelectric response at different magnetic fields. These magnetoelectric films are found to exhibit a negative tunneling magnetoresistance (TMR) effect with maximum TMR% of 28 for the film with 20 wt% of CoFe2O4 loading. The dielectric constant and electrical energy storage density of the films are increased with the addition of CoFe2O4 nanofiber. The ME films exhibiting TMR and high energy density can be the potential candidates for multifunctional device applications such as memory and spintronics devices, magnetic sensor, and bio-sensor.

Influence of Hydrothermally Synthesized Cubic-Structured BaTiO3 Ceramic Fillers on Ionic Conductivity, Mechanical Integrity, and Thermal Behavior of P(VDF–HFP)/PVAc-Based Composite Solid Polymer Electrolytes for Lithium-Ion Batteries

Solid polymer electrolytes (SPEs) with high ionic conductivity and wide electrochemical window are highly desirable for all-solid-state rechargeable lithium batteries. Herein, we report the use of ...

Enhanced electro-active phase in a luminescent P(VDF-HFP)/Zn2+ flexible composite film for piezoelectric based energy harvesting applications and self-powered UV light detection.

We have prepared a flexible polymer composite film containing poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and Zn2+ for the fabrication of a multifunctional piezoelectric based nanogenerator (MFNG), where a traditional electrical poling treatment was avoided. The desirable amount of Zn2+ yields more than 99% of electro-active phases in the P(VDF-HFP) matrix that co-operates to enhance the dielectric properties of the composite film via hydrogen bonding interactions. In situ thermal Fourier transform infrared (FT-IR) spectroscopy affirms the improved thermal stability of the electro-active β-phase and the β→γ phase transition temperature in the Zn2+ doped composite film. It also shows UV absorption and intense blue light emission confirmed by a CIE 1931 chart that gives it applicability as a flexible optical sensor. The MFNG behaves as an efficient mechanical energy harvester that delivers an open-circuit voltage ∼6 V and an output power of 2.4 μW and successfully enables the charging of a capacitor by simple repetitive finger touch and release motions (a pressure amplitude of ∼14 kPa). The UV light sensing ability of the MFNG is confirmed under the continuous application and removal of applied stress, which is very promising for designing versatile self-powered optoelectronic smart sensors. Our approach is very simple and cost effective for the construction of a new class of flexible multifunctional energy harvesters that have wonderful applications in the areas of piezo-photonics, wireless detection and flexible self-powered opto-electronics.

A surface-modified TiO2 nanorod array/P(VDF–HFP) dielectric capacitor with ultra high energy density and efficiency

A surface-modified TiO2 nanorod array/P(VDF–HFP) dielectric capacitor has an ultrahigh energy density of 17.5 J cm−3 at 509 kV mm−1.

Significantly enhanced energy storage density of sandwich-structured (Na0.5Bi0.5)0.93Ba0.07TiO3/P(VDF–HFP) composites induced by PVP-modified two-dimensional platelets

Layered composites involving NBBT platelets in a polymer matrix show excellent energy storage properties.

Investigation of relaxation process in poly(vinylidene fluoride–hexafluoropropylene) using dielectric relaxation spectroscopy

Dielectric relaxation behavior of poly(vinylidene fluoride–hexafluoropropylene) [P(VDF–HFP)] is investigated on the basis of dielectric relaxation spectroscopy at 20–200 °C and 20–5 MHz after conversion to complex electric modulus formalism. It is found that imaginary modulus spectra exhibit asymmetry peak with peak-width much broader than that of the Debye peak. The peaks are skewed toward the high frequency sides due to the effect of the conductivity. The complex electric modulus data have been fitted using non-exponent Kohlrausch–Williams–Watts and Cole–Cole functions. The results show that the non-exponent parameter (β) and the shape parameter (α) are all lower than idealized Debye-type, indicating a wide relaxation distribution of P(VDF–HFP). Both the activation energies Ea from $${\text{M}}^{\prime \prime }$$ spectra and conductivity are all due to the contribution of dc and ac conductive relaxation process.

Self‐poled Efficient Flexible “Ferroelectretic” Nanogenerator: A New Class of Piezoelectric Energy Harvester

AbstractSuperior ferro‐ and piezo‐electret properties in a self‐poled, porous hybrid ferroelectretic polymer nanocomposite film for next‐generation device paradigms is introduced by in situ generation of platinum (Pt) nanoparticles (NPs) embedded in poly(vinylidenefluoride‐co‐hexafluoropropylene) P(VDF–HFP). The cooperative functionality between the self‐polarized β‐phase and the micropores as charge trapping sites is realized by using a simple solvent evaporation method. As a consequence, the resulting film exhibits extraordinary ferroelectretic behavior, as demonstrated by the superior electrical square‐shaped hysteresis loop with large remnant polarization (Pr≈61.7 μC cm−2), piezoelectric charge coefficient (d33∼−686 pC N−1), and ultrahigh dielectric properties (εr=2678, tan δ=0.79 at 1 kHz). A new type of ferroelectretic nanogenerator (FTNG) is fabricated using a flexible hybrid nanocomposite film that effectively converts the applied mechanical energy into electrical energy upon compressive normal stress (e.g., by actuating with a human finger). The 18 V of the open‐circuit output voltage with expected 17.7 μA short‐circuit current are generated from the FTNG under 4 MPa of normal stress amplitude. The high piezoelectric energy conversion efficiency (ηpiezo≈0.2 %) of the FTNG shows that the hybrid polymer nanocomposite film is well suited for the next generation of piezoelectric‐based energy harvesters. The operation of more than 50 blue LEDs, 25 green LEDs, and several capacitors without any subsidiary batteries is demonstrated using the FTNG.

Tailoring microstructure and physical properties of poly(vinylidene fluoride–hexafluoropropylene) porous films

This paper presents a systematic study for the production of poly(vinylidene fluoride–hexafluoropropylene) [P(VDF–HFP)], porous films using solvent evaporation (SE) and non-solvent-induced phase separation (NIPS) techniques. Parameters such as volume fraction of the copolymer solution, film thickness, time exposure to air, non-solvent, and temperature of the coagulation bath were investigated on the morphology, crystallization, and mechanical properties of the samples. Films with different porous morphologies including homogeneous pore sizes, macrovoids, and spherulites were obtained depending on the processing conditions, which in turn affect the wettability and mechanical properties of the material. Knowing that the phase content of the films also depends on the processing conditions, this paper shows that P(VDF–HFP) films with tailored porous morphology, electroactive phase content, hydrophobicity, crystallinity, and mechanical properties can be achieved for a specific application using the adequate SE and NIPS techniques conditions.

Poly(vinylidene fluoride) nanofibrous mats with covalently attached SiO2 nanoparticles as an ionic liquid host: enhanced ion transport for electrochromic devices and lithium-ion batteries

Using ionic liquid-loaded SiO2-on-P(VDF–HFP) nanofibrous mats as electrolytes, both electrochromic devices and Li/LiCoO2 batteries exhibit significantly improved performance.

Impact of preparation method on physical properties and gas separation performance of fluorinated copolymer membranes

Two batches of poly(vinylidene fluoride–hexafluoropropylene) [P(VDF–HFP)] copolymer with different monomer ratios were thoroughly characterised and cast into membranes to relate the fundamental properties of this copolymer with its performance in CO2 separation. Solubility testing revealed that the PVDF part of the copolymer was dominating and calculations with Hansen’s solubility parameters corroborated the outcome. A very slow solvent evaporation rate and use of solvents with a high boiling point were found to be essential in the formation of defect-free membranes from this copolymer for gas separations. Physical examination, DSC, XRD and TGA were also performed to better link the fundamental membrane properties to the gas separation performance. A low crystallinity in the prepared P(VDF–HFP) membranes was favourable in terms of compatibility, solubility, membrane formation and CO2 separations.