Vinylidene Fluoride-co-hexafluoropropylene) (P Research Articles

Concurrently enhanced mechanical properties and capacitive performance in all-organic dielectric polymer blend via phase separation

Phase separation of polymer blends has attracted much interest in designing high-performance materials with specific mechanical and dielectric properties. To this end, three types of poly(methacrylic ester)s, including poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), and poly(isobutyl methacrylate) [P(iBMA)], have been incorporated in the poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] matrix, respectively. As exemplified in P(VDF-HFP)/P(iBMA) blended films, a conspicuous phase separation is experimentally observed and the blended film presents an enhanced Young's modulus and a one-fold increment in the elongation over the pristine P(VDF-HFP). The excellent plasticity is benefited from the interfacial regions between the two phases, which could effectively pin the cracks and retard the slippage under deformation. Simultaneously, an ultra-high Weibull breakdown strength (∼774 MV/m) is obtained in the blends, benefiting from the improved Young's modulus and excellent plasticity. The blends are endowed with an excellent energy storage density (∼21 J/cm3 at 830 MV/m), along with an impressive cycling stability. In contrary, P(VDF-HFP)/PMMA and P(VDF-HFP)/PBMA blended films sacrifice the plasticity due to the scarcity of phase separation; therefore, even though Young's moduli have been improved, there is no remarkable improvement for breakdown strengths and energy storage performances. The experimental results are augmented by molecular dynamics simulations. This contribution provides a facile approach to develop high-performance polymer dielectric materials through a phase separation design and emphasize the importance of plasticity for breakdown strength.

Two-Dimensional Fillers Induced Superior Electrostatic Energy Storage Performance in Trilayered Architecture Nanocomposites.

Dielectric capacitors with ultrahigh power densities and fast charging/discharging rates are of vital relevance in advanced electronic markets. Nevertheless, a tradeoff always exists between breakdown strength and polarization, which are two essential elements determining the energy storage density. Herein, a novel trilayered architecture composite film, which combines outer layers of two-dimensional (2D) BNNS/poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) with high breakdown strength and an intermediate layer made of blended 2D MoS2 nanosheets/P(VDF-HFP) with large polarization, is fabricated using the layer-by-layer casting method. The insulating BNNS with a wide band gap is able to largely alleviate the distortion of the local electric field, thereby suppressing the leakage current and effectively reducing the conductivity loss, while the 2D MoS2 nanosheets act as microcapacitors in the polymer composites, thus significantly increasing the permittivity. A finite element simulation is carried out to further analyze the evolution process of electrical treeing in the experimental breakdown of the polymer nanocomposites. Consequently, the nanocomposites possess an excellent discharged energy density of 25.03 J/cm3 accompanied with a high charging/discharging efficiency of 77.4% at 650 MV/m, which greatly exceeds those of most conventional single-layer films. In addition, the corresponding composites exhibit an outstanding reliability of energy storage performance under continuous cycling. The excellent performances of these polymer-based nanocomposite films could pave a way for widespread applications in advanced capacitors.

Preparation and characterization of proton (H+) conducting solid blend polymer electrolytes based on PEO/P(VdF-HFP) incorporated with NH4SCN

A new H+ ion-conducting solid blend polymer electrolytes system comprising of Poly (ethylene oxide) (PEO) and Poly (vinylidene fluoride-co-hexafluoropropylene) P(VdF-HFP) and ammonium thiocyanate (NH4SCN) have been prepared using solution casting technique. The X-Ray Diffraction (XRD) study demonstrates that there is a decrease in crystalline peaks of polymer electrolytes by increasing NH4SCN salt. FT-IR analysis confirms the interaction between polymers and salt. Using complex impedance spectroscopy, electrical characteristics have been determined with a 42Hz to 1MHz frequency range. The electrical conductivity varies with temperature and shows Arrhenius behaviour. The activation energy decreases as the salt content is increased. Frequency-dependent conductivity, dielectric permittivity (ε′) modulus (M′), and Loss tangent (tanδ) analysis of the prepared polymer electrolytes is also carried out. Argand plots are used to investigate the dynamics of ion relaxation. To analyze the electrochemical behaviour of the electrolytes, linear sweep voltametric (LSV) and cyclic voltametric (CV) measurements are performed. Thus, it is confirmed that the prepared polymer electrolytes are suitable for energy storage devices.

Enhanced dielectric constant and suppressed electrical conductivity in polymer nanocomposite films via loading MXene/TiO2/MoS2 nanosheets

Conductor/polymer nanocomposites can achieve high dielectric constant with low filler loading, but conductive fillers come into contact with each other easily, resulting in the formation of conductive paths. In this work, MXene/TiO2/MoS2 nanosheets were prepared by one-step hydrothermal method, and MXene/TiO2/MoS2/poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) nanocomposite films were prepared by solution casting method. At 1 kHz, with an optimized MXene/TiO2/MoS2 nanosheets loading of 8.0 wt%, MXene/TiO2/MoS2/P(VDF-HFP) nanocomposite films achieve a high dielectric constant of 944 and maintain a low dielectric loss of 0.19. TiO2 and MoS2 semiconductive layers on the surface of MXene nanosheets can prevent the formation of conductive paths, and therefore, nanocomposite films possess suppressed electrical conductivity. Moreover, MXene/TiO2/MoS2 nanosheets can build more microcapacitor structures in nanocomposite films with higher filler loading, which further improves the dielectric constant of nanocomposite films. Finite element simulation shows that TiO2 and MoS2 semiconductive layers can lower the electric field intensity and polarization intensity at the interface between conductive fillers and polymer matrix. Herein, MXene/TiO2/MoS2/P(VDF-HFP) nanocomposite films possess not only excellent dielectric properties, but also excellent mechanical properties, which can be used as flexible dielectric materials in electronic packaging technology.

Energy conversion of electrostrictive poly(vinylidene fluoride-co-hexafluoropropylene)/Graphene composites

This study investigates energy-conversion properties of the electrostrictive polymer, poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), filled with graphene nanosheets (GNPs). The composites (i.e., P(VDF-HFP) and GNPs) were fabricated by using the solution casting method. The dielectric constant of these electrostrictive materials was measured to observe the energy conversion property with different frequencies using an LCR meter. Their mechanical properties were measured using a photonic sensor with varying various input vibrations and electric fields to calculate their electrostrictive coefficients. These characterized results revealed that dielectric constants and electrostrictive coefficients were significantly increased when GNPs fillers were filled higher. For the electrical property, the generating current, which was measured across these polymer films, increased proportionally with respect to the adding GNPs. In this obtained result, the main finding of P(VDF-HFP)/GNPs composites is a promising electrostrictive material for applications of electromechanical energy conversions in many smart-material systems.

Ferroelectric properties and breakdown strength of layer-by-layer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and polyurethane (PU) for energy storage application

Ferroelectric polymers are one of the next- generation pulsed capacitor materials for the potential application in capacitive energy storage. This polymer with higher saturated polarization, smaller remnant polarization, and higher electrical breakdown are the most promising candidates. In this work, the dielectric properties and energy storage capacity of the bilayer polymer films of Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and polyurethane (PU) were studied. These bilayer polymers were prepared by layer- by- layer method at the condition of variable layer thickness. The results show that the dielectric constants and the saturated polarization of the bilayer films increased, and bilayer films with P70/PU30 exhibit electrical high breakdown strength up to 379 V/μm. Moreover, enhanced energy storage density and the energy efficiency of the bilayer constrictors will be discussed for the capacitive energy storage polymers.

Structural, transport, morphological, and thermal studies of nano barium titanate–incorporated magnesium ion conducting solid polymer electrolytes

A new series of nanocomposite polymer electrolytes (NCPEs) was prepared using poly(vinylidene fluoride–co–hexafluoro propylene) P(VdF-HFP) as polymer, magnesium triflate (MgTr) as salt and nano-sized barium titanate (BaTiO3) (<100 nm) as nanofiller via traditional solution casting technique. Decrease in crystalline nature of the samples due to the incorporation of nano BaTiO3 was revealed through X-ray diffraction (XRD) analysis. From AC impedance spectroscopy, maximum conductivity of 4.11 × 10−4 Scm−1 was attained for the addition of 6 wt% of nano BaTiO3 to the P(VdF-HFP)/MgTr matrix. Dielectric studies were found to be in accordance with the ionic conductivity studies. For the most highly conducting sample, a greater number of mountain valley pattern was observed from Atomic Force Microscopy (AFM) analysis. Thermal stability of the sample, P(VdF-HFP)/MgTr/BaTiO3 (6 wt%) (which possessed maximum ionic conductivity) was observed through TG/differential thermal analysis studies. All these results suggested that these materials are favorable and find application in practical electrochemical devices.

Understanding Effects of Ion Diffusion on Charge Carrier Mobility of Electrolyte‐Gated Organic Transistor Using Ionic Liquid‐Embedded Poly(3‐hexylthiophene)

In electrolyte‐gated organic electronics, including electrochromic devices, organic field‐effect transistors, and organic electrochemical transistors, the underlying working principle is determined by the permeability of the electrochemically active ions within the electrolyte dielectric into the organic semiconductor layer; as such, the carrier mobility of organic semiconductors in electrolyte‐gated devices remains unclear because of the different degrees of ion penetration depending on the fabrication process and device architecture. Here, ion‐embedded organic semiconductors are developed by precisely incorporating ionic liquid (IL) in poly(3‐hexylthiophene) (P3HT), and then the effects on the charge carrier mobility in organic transistors using poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride‐co‐hexafluoropropylene) (P(VDF‐HFP)) and electrolyte dielectrics are systematically investigated. Neat P3HT transistors show saturation mobility of 0.080 ± 0.003, 0.287 ± 0.025, and 5.04 ± 0.16 cm2 V−1 s−1 using PMMA, P(VDF‐HFP), and polymer electrolyte dielectrics, respectively. Compared with control neat P3HT devices, nonproportional normalized saturation mobilities of 0.46 (0.30), 1.65 (1.35), and 0.74 (0.89) are observed for P3HT:IL of 99.5:0.5(98:2) v/v% devices using PMMA, P(VDF‐HFP), and polymer electrolyte dielectrics, respectively. In addition, it is found that the ion penetration into P3HT can influence the metal/semiconductor contact and interfacial charge trapping at the dielectric/semiconductor, which can disrupt the efficient charge carrier transport.

Polymer Nanocomposites with High Energy Density Utilizing Oriented Nanosheets and High-Dielectric-Constant Nanoparticles.

The development of high-energy-density electrostatic capacitors is critical to addressing the growing electricity need. Currently, the widely studied dielectric materials are polymer nanocomposites incorporated with high-dielectric-constant nanoparticles. However, the introduction of high-dielectric-constant nanoparticles can cause local electric field distortion and high leakage current, which limits the improvement in energy density. In this work, on the basis of conventional polymer nanocomposites containing high-dielectric-constant nanoparticles, oriented boron nitride nanosheets (BNNSs) are introduced as an extra filler phase. By changing the volume ratios of barium titanate (BT) and BNNSs, the dielectric property of polymer nanocomposites is adjusted, and thus the capacitive energy storage performance is optimized. Experimental results prove that the oriented BNNSs can suppress the propagation of charge carriers and decrease the conduction loss. Using poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) as the polymer matrix, the P(VDF-HFP)/BNNS/BT nanocomposite has a higher discharged energy density compared with the conventional nanocomposite with the freely dispersed BT nanoparticles.

Transport of Propylene Carbonate-LiTFSI Electrolytes in P(VDF-HFP) Using Time-resolved ATR-FTIR Spectroscopy: Diffusion Coefficients and Molecular Interactions

The time-resolved attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is employed to investigated the transport mechanism of gel electrolytes by monitoring the diffusion behavior of propylene carbonate-lithium bis(trifluoromethylsulfonyl)imide (PC-LiTFSI) solution through poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) films. Fickian behavior has been observed for both TFSI- and PC. Higher temperature leads to faster diffusion of TFSI- and PC, which could be related to the increased free volume in P(VDF-HFP) matrix and rapid molecular movements upon heating. Various molecular interactions among LiTFSI, PC and P(VDF-HFP) have been recognized. During the diffusion process, PC molecules, in the form of small clusters, can firstly diffuse through the P(VDF-HFP) film and interact with P(VDF-HFP) by dipole-dipole interaction, acting as the plasticizer. Then, Li+ diffuses into P(VDF-HFP) with the help of ion-dipole interactions between Li+ and C=O of PC. Meanwhile, TFSI- diffuses through the polymer matrix in solvation states. In addition, slight ion-dipole interactions between Li+ and P(VDF-HFP) have been observed as well. Results in this work contribute to a better understanding of transport process in gel polymer electrolytes for lithium-ion batteries and support the development of improved gel polymer electrolytes by rationally regulating molecular interactions.

High-performance sandwiched hybrid solid electrolytes by coating polymer layers for all-solid-state lithium-ion batteries

Poly(vinylidenefluoride-co-hexafluoropropylene) (P(VDF-HFP))/Li1.3Al0.3Ti1.7(PO4)3 (LATP)/P(VDF-HFP) sandwiched hybrid solid electrolytes were precisely tailored and successfully fabricated to assemble into all-solid-state lithium-ion batteries, which were systematically evaluated on microstructure, morphology, thermal stability and electrochemical performance. The sandwiched hybrid solid electrolytes can achieve intimate contact with cathode and anode electrodes to present an excellent interfacial stability. Furthermore, the sandwiched hybrid solid electrolytes possess flexible surface, wide electrochemical working window of 4.7 V, high ionic conductivity of 0.763 mS·cm−1 and high thermal stability of 460 °C, which may contribute to realizing the practical application in all-solid-state lithium-ion batteries. The assembled cells with the hybrid solid electrolytes can quickly stabilize at a specific discharge capacity of 145.4 mAh·g−1 at 0.1C after only 5 cycles and present admirable rate performance. In addition, morphology characterizations of the sandwiched hybrid solid electrolytes after long-term cycles show a relatively integrated structure coating with a compact LATP layer. The investigations afford a promising strategy that the sandwiched hybrid solid electrolytes can overcome the mechanical limitations of the interface between electrodes and inorganic solid electrolytes to provide favorable properties for all-solid-state lithium-ion batteries.

Novel P(VDF-HFP)/BST nanocomposite films with enhanced dielectric properties and optimized energy storage performance

Nanocomposites using poly (vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), as the matrix, and barium strontium titanium oxide (BST) nanoparticles as the filler were systematically studied. P(VDF-HFP)/BST composite films containing different amounts of BST were prepared using the solution-casting method. The dielectric constant (εr), dielectric loss (tan δ), and their frequency and temperature dependence, were characterised for the films under weak electric fields. The behaviour of the films under high electric fields was explored using polarisation-electric field (P-E) loops. The εr was found to increase from 14.1 to 42.1 as the BST content increased from 0 vol% to 40 vol%, and the Maxwell-Wagner model showed a good fit with the measured εr values, indicating that the microstructure of the fabricated nanocomposites is uniform, which can also be observed in SEM images of all P(VDF-HFP)/BST nanocomposite films. In determining the temperature (T) dependence of the εr and tan δ of the composites, P(VDF-HFP) plays a decisive role, while BST plays an influential role. As the BST content increases, the charge/discharge energy density (Ucharge/Udischarge) increases, while the breakdown strength (Eb) and charge-discharge efficiency (η) decrease. Notably, the maximal Udischarge 3.79 J/cm3 was obtained when the BST content was 20 vol% at 2100 kV/cm. In addition, from the perspective of practical application, when the applied electric field intensity is lower than 900 kV/cm or between 900 kV/cm and 2100 kV/cm, in order to obtain the maximal Udischarge, the P(VDF-HFP)/BST composite with BST content of 30 vol% or 20 vol% should be selected respectively.

Structure design boosts concomitant enhancement of permittivity, breakdown strength, discharged energy density and efficiency in all‐organic dielectrics

Polymer-based nanocomposites with excellent flexibility and intrinsic high breakdown strength are promising candidates for high energy density capacitors compared to ceramics counterparts. However, their energy density is relatively low due to the trade-off between permittivity and breakdown strength. In this work, the authors proposed a ferroconcrete-like structure for all-organic nanocomposites via combinatorial electrospinning and hot-pressing method. In this structure, polymethyl methacrylate (PMMA) serves as matrix while poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) serves as reinforcement phase. This novel structure is highly effective in breaking the paradox of improved discharged energy density with decreased efficiency, as evidenced by the concurrently improved discharged energy density (∼12.15 J/cm3 compared to 8.82 J/cm3 of the matrix) and efficiency (∼81.7% compared to 76.8% of the matrix). Compared to conventional blending composite films, samples with ferroconcrete-like structure exhibit higher permittivity, breakdown strength, discharged energy density and efficiency. The superior energy storage performance is attributed to large aspect ratio P(VDF-HFP) fibres distributed perpendicularly to the external field, which brings about the extra enhancement of permittivity. Besides, mechanical properties are improved and restriction on carrier motion is facilitated, leading to enhanced breakdown strength and suppressed conduction. This work provides a new way to design dielectric composite for high energy density and efficiency applications.

Physical and electrochemical chattels of phosphonium ionic liquid-based solid and gel-polymer electrolyte for lithium secondary batteries

In this work, a methodical study on the influence of ionic conductivity on polymer electrolyte with different weight percentages of ionic liquid and plasticizers had been investigated in detail. Solution casting method has been employed for preparing polymer electrolyte (PE) blend having poly(vinylidenefluoride-co-hexafluoropropylene) P(VdF-co-HFP) as polymer, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) amide [P14,6,6,6][Tf2N] as ionic liquid and ethylene carbonate (EC) as well as propylene carbonate (PC) in 1: 1 ratio as plasticizers. The polymer electrolyte has been found out stable up to 450 °C, as measured from Thermal gravimetric analysis (TGA). Impedance spectral analysis reveals that the ionic conductivity of SPEs is 3.209 × 10–6 S/cm at 303 K with 25 wt% of ionic liquid. The addition of plasticizers (EC + PC (60 wt%)) results in two orders of magnitude of higher ionic conductivity (3.40 × 10–4 S/cm at 303 K), than that of SPEs. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are performed to study the physico-chemical characteristics of polymer electrolytes. Electrochemical stability, potential window and discharge characteristics of the coin cell containing the electrolytes and LiFePO4 electrode were investigated using linear and cyclic voltammetry.

Achieving superior energy density in ferroelectric P(VDF-HFP) through the employment of dopamine-modified MOFs

Dielectric polymer/composites films with excellent capacitive performance has initiated enormous interest from both academic and industry because of their great potential as flexible and light-weight electrostatic capacitors for modern electric and electronic systems. In this work, we report a novel flexible dielectric composite film consisting of poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and dopamine-modified metal-organic frameworks Co3 [Co(CN)6]2 (D-M) with excellent capacitive performance for energy storage application. It is found that the D-M show good compatibility with P(VDF-HFP), permitting a high breakdown strength for composites. Meanwhile, the large specific surface area and special porous three-dimensional nanostructure of D-M also has the effect of raising dielectric performance while eliminating the inherent ferroelectric loss of P(VDF-HFP), resulting in considerably promoted discharge energy density. Furthermore, D-M is found to favor the formation of γ-phase in P(VDF-HFP), which is also advantageous to raise the discharge energy density. Upon a small loading of 0.6 wt% D-M, the composites perform a maximum discharge energy density of 11.89 J/cm3 and discharge efficiency of 71.28% at 350 MV/m, which are 3.04 times and 1.25 times those of the pure P(VDF-HFP) film, respectively. For the first time, we demonstrate that the applicability of flexible D-M/P(VDF-HFP) dielectric composites as advanced electrostatic capacitors, providing a new sight for the design of dielectrics with high capacitive performance.

Evaluation of Self-Assembly Pathways to Control Crystallization-Driven Self-Assembly of a Semicrystalline P(VDF-co-HFP)-b-PEG-b-P(VDF-co-HFP) Triblock Copolymer.

To date, amphiphilic block copolymers (BCPs) containing poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-co-HFP)) copolymers are rare. At moderate content of HFP, this fluorocopolymer remains semicrystalline and is able to crystallize. Amphiphilic BCPs, containing a P(VDF-co-HFP) segment could, thus be appealing for the preparation of self-assembled block copolymer morphologies through crystallization-driven self-assembly (CDSA) in selective solvents. Here the synthesis, characterization by 1H and 19F NMR spectroscopies, GPC, TGA, DSC, and XRD; and the self-assembly behavior of a P(VDF-co-HFP)-b-PEG-b-P(VDF-co-HFP) triblock copolymer were studied. The well-defined ABA amphiphilic fluorinated triblock copolymer was self-assembled into nano-objects by varying a series of key parameters such as the solvent and the non -solvent, the self-assembly protocols, and the temperature. A large range of morphologies such as spherical, square, rectangular, fiber-like, and platelet structures with sizes ranging from a few nanometers to micrometers was obtained depending on the self-assembly protocols and solvents systems used. The temperature-induced crystallization-driven self-assembly (TI-CDSA) protocol allowed some control over the shape and size of some of the morphologies.

Transparent Stretchable Dual-Network Ionogel with Temperature Tolerance for High-Performance Flexible Strain Sensors.

A stretchable transparent double network ionogel composed of physically cross-linked poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) and chemically cross-linked poly(methyl methacrylate-co-butylmethacrylate) (P(MMA-co-BMA)) elastomer networks within [EMIM][TFSI] ionic liquid was fabricated through a facile one-pot thermal polymerization. The dual-network (DN) ionogel presents good mechanical performance (failure tensile stress 2.31 MPa, strain 307%) with a high loading of ionic liquid (70 wt %) for achieving required ionic conductivity (>0.1 S/m at room temperature). The transparent chemical cross-linked P(MMA-co-BMA) elastomer network endows high transparency (>93%) and high stretchability to the DN ionogel. The DN ionogel maintains good toughness, elasticity, and transparency in a wide temperature range (-40 to 80 °C) for the application in a harsh environment. In addition, the sensitivity of the DN ionogel to the change of environment temperature and deformation was detected and described. The practical potential of the DN ionogel in flexible electronic devices is further revealed by fabricating DN ionogel strain sensors to detect the movement of different human limbs including the bending of the finger, wrist, and elbow as well as the slight throat jitter during the swallowing and vocalization, showing fast response, high sensitivity, and good repeatability.

Thermal and combustion behavior of Al-MnO2 nanothermite with poly(vinylidene fluoride -co- hexafluoropropylene) energetic binder

Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content. To explore the effect of poly(vinylidene fluoride -co- hexafluoropropylene) (P(VDF-HFP)) on Al/MnO2 nanothermite, the samples with different contents are prepared and characterized by SEM, TG-DSC, XRD, and their ignition and combustion behavior are tested and recorded. The results show that P(VDF-HFP) as an energetic binder can combine the nanothermite components together, even exist in the gaps. The integrity of energetic materials has been improved. Thermal analysis shows that the addition of P(VDF-HFP) greatly changes the thermal reaction processes, and the exothermic peaks appear early, but the utilization of fuel and oxidizer is not efficient from the XRD results. Furthermore, the appropriate addition of P(VDF-HFP) can directly reduce the ignition energy threshold and increase the combustion time, which is necessary for the potential ignition charge application. The possible reasons for above phenomena are discussed and analyzed. This research provides a reference for improvement of thermite-based ignition charge formulation.

Ultrahigh Energy Efficiency and Large Discharge Energy Density in Flexible Dielectric Nanocomposites with Pb0.97La0.02(Zr0.5SnxTi0.5-x)O3 Antiferroelectric Nanofillers.

Flexible dielectric capacitors have been widely studied recently on account of their fast charge-discharge speed, high power density, and superior wearable characteristics. Inorganic ferroelectric fillers/polymer matrix composites combining large maximum electric displacement (Dmax) of ferroelectric materials with good flexibility and high electric breakdown strength (Eb) of the polymer are regarded as the most promising materials for preparing flexible dielectric capacitors with superior energy storage properties. However, simultaneously achieving large discharge energy density (Wd) and high energy efficiency (η) in these composites remains challenging on account of a large remnant electric displacement (Dr) and low Dmax - Dr values of ferroelectric fillers. In contrast, antiferroelectrics (AFEs) exhibit near zero Dr and larger Dmax - Dr values and are thus attractive composite fillers to simultaneously achieve large Wd and high η. On the basis of these factors, in this report, we design and prepare Pb0.97La0.02(Zr0.5SnxTi0.5-x)O3 (PLZST) AFE nanoparticles (NPs)/poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) nanocomposites and investigate the effects of the Sn and AFE NPs contents on the energy storage capacity of the nanocomposites. Through reasonable adjustment of the Sn content and the PLZST AFE fillers content, because of the large Dmax - Dr value of 7.75 μC/cm2 and small Dr value of 0.26 μC/cm2 at the Eb as high as 3162 kV/cm, the Pb0.97La0.02(Zr0.5Sn0.38Ti0.12)O3 AFE NPs/P(VDF-HFP) polymer nanocomposite with 7 wt % fillers exhibits the most superior energy storage properties with an ultrahigh η of 93.4% and a large Wd of 12.5 J/cm3. These values are superior to those of the recently reported dielectric nanocomposites with a single-layer structure containing ferroelectric nanowires, nanofibers, nanobelts, nanotubes, and nanosheets or core-shell structure fillers, which are prepared via a very complicated method. This work not only shows that, in principle, the polarization characteristics of the composites depend mainly on those of the inorganic fillers but also demonstrates a convenient, effective, and scalable way to fabricate dielectric capacitors with superior flexibility and energy storage capacities.

Lithium garnet incorporated 3D electrospun fibrous membrane for high capacity lithium-metal batteries

A new class of electrolytes with enhanced flexibility, high lithium ion (Li+) conductivity, excellent electrochemical stability, good cyclic ability and improved safety are crucial for high performance of lithium-metal batteries. Composite polymer electrolytes assist in overwhelming safety-related issues faced by Li+ batteries with organic liquid electrolytes. Herein, we report on polymer nanocomposite electrospun fibrous membranes (PNEFM) comprising of Li6.28Al0.24La3Zr2O12 (LLZA) garnet oxide nano-fillers in poly (vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) co-polymer prepared by electrospinning technique. Li+ conductivity of the PNEFM is remarkably improved by the addition of LLZA garnet filler. The PNEFM-8 (with 8 wt% of LLZA) exhibits a maximized Li+ conductivity of 2.25 × 10−3 S cm−1 at room temperature (25 °C). The PNEFM-8 exhibits a wide electrochemical potential window up to 5.5 V. A full cell with Li||PNEFM-8||LiFePO4 configuration at 25 °C displayed first discharge capacity of 160 mA h g−1 and a reversible discharge capacity of 145 mA h g−1 for 100th cycle at 0.1 C with Coulombic efficiency of 98.78%. Furthermore, PNEFM-8, integrated with composite sulphur cathode exhibits an excellent first discharge capacity of 1311 mA h g−1 and a reversible discharge capacity of 1105 mA h g−1 after 10th cycles with 98.30% Coulombic efficiency. The present study could contribute towards the development of higher performance and safe room temperature Li-metal batteries.