Enhanced dielectric performance of BaTiO3/PVDF composites prepared by modified process for energy storage applications

Structural, Mechanical, and Barrier Properties of the Polyvinylidene Fluoride-Bacterial Nanocellulose-Based Hybrid Composite

This study presents an analysis of films which consist of two layers; one layer is PVDF as the matrix, along with fillers BaTiO3 (BT), and the second is one bacterial nanocellulose (BNC) filled with Fe3O4. The mass fraction of BT in PVDF was 5%, and the samples were differentiated based on the duration of the mechanical activation of BT. This innovative PVDF laminate polymer with environmentally friendly fillers aligns with the concept of circular usage, resulting in a reduction in plastic content and potential improvement of the piezoelectric properties of the entire composite. This work presents new, multifunctional "green" packaging materials that potentially could be a good alternative to specific popular materials used for this purpose. The synthesis of the films was carried out using the hot press method. Tensile tests, water vapor permeability examination, and structural analyses using SEM-EDS and FTIR have been conducted. The sample PVDF/BT20/BNC/Fe3O4 exhibited the best barrier properties (impermeability to water vapor), while the highest tensile strength and toughness were exhibited by the PVDF/BT5/BNC/Fe3O4 sample.

Piezoelectric Nanogenerators Fabricated Using Spin Coating of Poly(vinylidene fluoride) and ZnO Composite

In this context, the open-circuit voltage generated by either poly (vinylidene fluoride) or PVDF and ZnO composite sample before being enhanced to 4.2 V compared to 1.2 V for the samples of pure PVDF. The spin coating method was used to create a composite film, which served as a piezoelectric nanogenerator (PNG). Zinc oxide (ZnO) nanoparticles and PVDF serve as the matrix for the coating structure. Thin films were created that employed the spin coating method to achieve the desired results of ZnO's non-brittle outcome and piezoelectric characteristics, as well as PVDF for use in self-powered devices. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and fourier transform infrared (FT-IR) were used to evaluate the properties of these formations. The electrical properties of the film were measured using an oscilloscope. Results indicated that by adding ZnO nanoparticles to the PVDF samples, piezoelectric capabilities were enhanced compared to samples containing PVDF only. These results point to promising uses for various wearable devices, such as water strider robot systems and self-operating equipment.

Designer Peptide-PVDF Composite Films for High Performance Energy Harvesting

Polymers and peptides have recently been considered as promising materials for piezoelectric energy harvesting because of their biocompatibility and enormous design possibility. However, achieving significant output voltages while meeting environmental safety requirements, low-cost and easy fabrication remains a major challenge. Herein, we have fabricated a lipidated pseudopeptide incorporated poly(vinylidene fluoride) (PVDF) composite films. Adding lipidated pseudopeptide (BLHA) increases the electroactive phase content, reaching the maximum for the 2 wt% composite film. The composite film containing 2 wt% BLHA manifests the highest dielectric constant and remnant polarization (P_r ), among others. A piezoelectric energy harvesting device fabricated with this film generates open-circuit output voltages up to 23 V, five times amplified output compared to pure PVDF. To the best of our knowledge, this material is superior among the peptide-based piezoelectric energy harvesters reported in the literature. The device is flexible, durable, low-cost, and sensitive to high and low pressures. It can power up multiple LCD panels when pressed with a finger. The non-covalent interaction between BLHA and PVDF is the reason behind the composites' improved piezoelectric response. Density functional theory (DFT) calculations also support this notion. This article is protected by copyright. All rights reserved.

Obtaining Greatly Improved Dielectric Constant in BaTiO3-Epoxy Composites with Low Ceramic Volume Fraction by Enhancing the Connectivity of Ceramic Phase

Ceramic-polymer dielectric composites show promising potential as embedded capacitors, whereas it is a great challenge to obtain a high dielectric constant (ε_r) at a low ceramic volume fraction (V_c). This work demonstrates a strategy for overcoming this challange. By employing a high sintering temperature (T_s) and introducing porogen, BaTiO₃ ceramics with both great connectivity and high porosity are obtained, and the composites with improved ε_r at a low V_c are prepared after curing the epoxy monomer, which is infiltrated into the porous ceramic bodies. For the composite with a T_s of 1300 °C and a V_c of 38.1%, the ε_r is as high as 466.8 at 1 kHz, which is improved by about nine times compared to the 0-3 counterpart with a higher V_c of 60.8%. Furthermore, the composite exhibits low dielectric loss and good frequency and temperature stability of ε_r, indicating the great potential for practical applications. Finite element simulation shows that the enhanced connectivity of BaTiO₃ increases the electric field intensity in high-ε_r BaTiO₃ dramatically and therefore plays a key role in the dielectric response of the composite. This work not only sheds light on the high-ε_r ceramic-polymer composites but also deepens the understanding on the relationship between their properties and microstructures.

A study on electroactive PVDF/mica nanosheet composites with an enhanced γ-phase for capacitive and piezoelectric force sensing

Herein, a multifunctional poly(vinylidene fluoride) (PVDF)/mica nanosheet composite (PMNC) thin film was developed for preparing a capacitive and piezoelectric force sensor. A high electroactive γ-phase content (89%) of PVDF was achieved through a facile rapid cooling process of PMNC films. The crystallinity of PVDF decreased upon the addition of mica nanosheets, while the dielectric constant increased significantly (∼300%). The capacitance-based PMNC pressure sensor was found to be sensitive to the applied pressure. On the other hand, piezoelectric voltages of 18 V (single layer) and 32 V (multi-layer) were generated for PMNCs loaded with 1% mica nanosheets. Furthermore, a PMNC based nanogenerator generated a power density of 8.8 μW cm^-2 and showed excellent durability (>60 000 cycles). High flexibility, lightweight and skin-friendly PMNCs could be a potential material in applications such as energy harvesting, energy storage, actuators, and self-powered and smart wearable electronic devices.

A fully sustainable, self-poled, bio-waste based piezoelectric nanogenerator: electricity generation from pomelo fruit membrane

A self-powered system is very much essential aspect in the recent trend to improve the working efficiency of the portable and wearable devices. Here, we have reported a fully sustainable, self-poled, bio-compatible, and bio-waste based piezoelectric energy harvester which has been made of Pomelo Fruit Membrane (PFM). PFM based piezoelectric generator (PFMBPEG) could generate ~ 6.4 V output voltage and ~ 7.44 μA output current directly, only by finger tapping on the device and registers a power density of ~ 12 μW cm-2 whereas, the same piezoelectric generator can generate ~ 15 V output voltage, 130 μA output current, and power density of ~ 487.5 μW cm-2 by using a full wave rectifier. The sensitivity and energy harvesting competence of the generator have also been assessed by attaching this nanogenerator into various parts of human body (as energy sources) such as wrist, elbow, finger, throat, jaws, leg and putting the device into ultrasonic bath and in every case, it could successfully generate voltage. Therefore, this bio-waste based energy harvester can be used as a power source for the different potable and wearable electronic goods where a small amount of energy is required, specifically in the biomedical applications (i.e., health monitoring, power source for the implantable devices and so on). Finally, mechanical stability the developed piezoelectric generator has been evaluated by cyclic bending test and it has been observed that there is no significant deformation of the PFM film even after 100 cycles.

Investigating the role of carbon nanotubes (CNTs) in the piezoelectric performance of a PVDF/KNN-based electrospun nanogenerator

In the present study, the effect of varying the concentration of carbon nanotubes (CNTs) on the piezoelectric performance of a poly(vinylidene fluoride) (PVDF)/potassium sodium niobate (KNN)-based electrospun nanocomposite has been revealed. The incorporation of 0.1% CNTs in the PVDF/KNN composite results in a significant improvement in the performance of the nanogenerator, with an output voltage of ∼23.24 V, a current of ∼9 μA and a power density of 52.29 μW cm^-2 under finger tapping compared with a voltage of ∼12 V, a current of ∼18 μA and a power density of 54 μW cm^-2 upon the application of a mechanized compressive force. In fact, the addition of CNTs led to a higher β-fraction in the hybrid nanocomposite. Moreover, the presence of CNTs creates a conducting path in the nanofiller loaded polymer jet, which results in enhanced mechanical stretching of the electrospun fibres. This hybrid lead-free nanogenerator could be a good candidate for use in self-powered portable and wearable electronic goods where a very small amount of power is required.

Interface-Dominated Time-Dependent Behavior of Poled Poly(Vinylidene Fluoride-Trifluoroethylene)/Barium Titanate Composites

Composites in which particles of ferroelectric ceramic phase are randomly dispersed in a polymeric matrix are of interest because of flexibility, conformability, and ease of processing. However, their piezoelectric properties are rather low, unless very high volume fractions of ceramics are used. This brings agglomeration and porosity issues due to the large mismatch between the surface energies of the ceramics and of the polymer. Particle surface modification is a common approach for better dispersion; however, it may bring other effects on the properties of the composites, which are usually concealed by the huge improvement in performance due to the more homogenous microstructure. In this work, we compared poly(vinylidene fluoride–trifluoroethylene)/barium titanate composites containing 15 vol.% and 60 vol.% of pristine ceramic particles or particles modified with an aminosilane or a fluorosilane. Similar morphology, with good particle dispersion and low porosity, was achieved for all composites, owing to an efficient dispersion method. The materials were poled with two different poling procedures, and the piezoelectric coefficient d₃₃, the relative permittivity, and the poling degree of barium titanate were followed in time. We highlighted that, although similar d₃₃ were obtained with all types of particles, the nature of the particles surface and the poling procedure were associated with different charge trapping and influenced the evolution of d₃₃ with time.

Interfacial engineering tailoring the dielectric behavior and energy density of BaTiO3/P(VDF-TrFE-CTFE) nanocomposites by regulating a liquid-crystalline polymer modifier structure

Dielectric polymer-based nanocomposites have attracted significant attention in recent years for energy storage applications because of their potential high permittivity and breakdown strength. The coupling effect of a nanofiller/matrix interface plays a crucial role in the dielectric and electric properties of polymer-based nanocomposites. In this paper, three kinds of side-chain liquid crystalline fluoric-polymers, denoted as P-nF (n = 3, 5 or 7, which is the number of terminal fluoric groups), were grafted on the surface of BaTiO3 nanoparticles by a surface-initiated reversible-addition-fragmentation chain transfer polymerization method. The nanocomposite films were prepared via core-shell BaTiO3 nanoparticles dispersed in a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) P(VDF-TrFE-CTFE) polymer matrix. The frequency dependent dielectric properties and energy storage capability of the polymer nanocomposites were studied. The results showed that the permittivity and energy densities of the polymer nanocomposites depended on the molecular structure of the modifier, especially the number of electron-rich fluoric groups. Firstly, all modified BaTiO3 nanoparticles were homogeneously dispersed in the polymer matrix, resulting in the polymer nanocomposites presenting a higher breakdown strength compared with the unmodified BaTiO3 nanoparticles. Secondly, the changes in the nanocomposites' permittivity exhibited diversity for three modifiers due to many influential factors. Thirdly, compared with neat P(VDF-TrFE-CTFE), the discharge energy densities of the polymer nanocomposites are all significantly improved. The highest discharge energy densities of nanocomposites with 5 vol% P-3F@BT reached 14.5 J cm-3. These findings suggest that the optimal interfacial modifier should be carefully decided by combining various properties of the nanocomposites for energy storage.

Particle size effect of BaTiO3 nanofillers on the energy storage performance of polymer nanocomposites

Polymer nanocomposites are a promising substitute for energy-storage dielectric materials in pulsed power systems. A barium titanate/polyvinylidenefluoride (BT/PVDF) nanocomposite is one of the most widely studied composite systems due to its comprehensive excellent dielectric properties. As the dielectric response of nanocomposites depends strongly on the size of the fillers, in this study, BT/PVDF nanocomposites with 92.3 nm, 17.8 nm and 5.9 nm BT particle fillers are fabricated to reveal the particle size effect of the fillers on the energy storage performance of the polymer nanocomposites. Owing to the small particle size and good dispersibility of the nanofillers, the nanocomposites with smaller BT particles show more uniform and denser microstructures. Moreover, with the increase of the filler fraction, the dielectric results indicate a breakdown strength enhancement in the nanocomposites with sub-20 nm BT fillers, which is quite different from the nanocomposites with normal fillers, and therefore leads to superior energy storage performance. This study provides experimental evidence for the application of ultrafine nanofillers in the nanocomposite for future energy storage systems.

One-Step Solvent Evaporation-Assisted 3D Printing of Piezoelectric PVDF Nanocomposite Structures

Development of a 3D printable material system possessing inherent piezoelectric properties to fabricate integrable sensors in a single-step printing process without poling is of importance to the creation of a wide variety of smart structures. Here, we study the effect of addition of barium titanate nanoparticles in nucleating piezoelectric β-polymorph in 3D printable polyvinylidene fluoride (PVDF) and fabrication of the layer-by-layer and self-supporting piezoelectric structures on a micro- to millimeter scale by solvent evaporation-assisted 3D printing at room temperature. The nanocomposite formulation obtained after a comprehensive investigation of composition and processing techniques possesses a piezoelectric coefficient, d₃₁, of 18 pC N^-1, which is comparable to that of typical poled and stretched commercial PVDF film sensors. A 3D contact sensor that generates up to 4 V upon gentle finger taps demonstrates the efficacy of the fabrication technique. Our one-step 3D printing of piezoelectric nanocomposites can form ready-to-use, complex-shaped, flexible, and lightweight piezoelectric devices. When combined with other 3D printable materials, they could serve as stand-alone or embedded sensors in aerospace, biomedicine, and robotic applications.

Improving Dielectric Properties of PVDF Composites by Employing Surface Modified Strong Polarized BaTiO₃ Particles Derived by Molten Salt Method

BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers-based nanocomposites filled with ferroelectric particles to achieve desirable dielectric properties.

Effect of the Modifier Structure on the Performance of Barium Titanate/Poly(vinylidene fluoride) Nanocomposites for Energy Storage Applications

Surface modification on ceramic fillers is of interest to help improve their compatibility in ceramic/polymer nanocomposites and, if possible, to control the influence of modifiers on the performance of the nanocomposites. In this paper, four kinds of small-molecule modifiers were chosen to treat the surface of BT nanoparticles, and the PVDF-based nanocomposites filled with the modified BT nanoparticles were prepared. The influences of modifiers on compatibility, permittivity, breakdown strength and polarization have been systematically investigated in order to identify the optimal surface modifier to enhance the energy density of the nanocomposites. Due to different structures (including type, number, and position of functional groups in molecules), the modifiers show different effects on the permittivity of the nanocomposites, while the breakdown strengths are all significantly improved. Consequently, the discharged energy densities of nanocomposites modified by 2,3,4,5-tetrafluorobenzoic acid and phthalic acid increase 35.7% and 37.7%, respectively, compared to BT/PVDF, indicating their potential as high energy density capacitors.

Fluorocarboxylic acid-modified barium titanate/poly(vinylidene fluoride) composite with significantly enhanced breakdown strength and high energy density

Fluorocarboxylic acid, as a novel surface modifier for BT nanoparticles, has significantly improved the performance of the BT/PVDF composites.

Uniform distribution of low content BaTiO3 nanoparticles in poly(vinylidene fluoride) nanocomposite: toward high dielectric breakdown strength and energy storage density

The uniform distribution of low content nanofillers in polymer nanocomposites was achieved to maximize energy storage with improved breakdown strength and simultaneously increased the relative dielectric constant.