Polyvinylidene Fluoride Polymer Research Articles

Piezoelectric Nanogenerator Based on Electrospinning PVDF/Cellulose Acetate Composite Membranes for Energy Harvesting.

The organic piezoelectric polymer polyvinylidene fluoride (PVDF) has attracted extensive research because of its excellent flexibility and mechanical energy-harvesting properties. Here, the electrospinning technique was taken to fabricate synthesized fiber membranes of a PVDF/cellulose acetate (CA) composite. The obtained PVDF/CA electrospun fiber membranes (EFMs) were employed to prepare a flexible nanogenerator. XRD and FTIR spectroscopy revealed the enhancement of piezoelectric behavior due to an increase in β-phase in PVDF/CA EFMs compared with cast films. The PVDF/CA fibers (mass ratio of PVDF to CA = 9:1) showed an output voltage of 7.5 V and a short-circuit current of 2.1 μA under mechanical stress of 2 N and frequency of 1 Hz, which were 2.5 and two times greater than those of the pure PVDF fibers, respectively. By charging a 4.7 µF capacitor for 15 min with the voltage generated by the PVDF/CA EFMs, nine LED lamps could be lit. The work provides an effective approach to enhancing the piezoelectric effects of PVDF for low-power electronic loading of macromolecule polymers.

Electrochemical and Structural Study on PVDF-Based Polymer Electrolytes for Solid-State Batteries

Lithium-ion batteries are widely used today in powering devices from portable electronics to electric vehicles. Despite their great success, this battery chemistry relies on organic solvent-based liquid electrolytes which are highly flammable, leading to major safety concerns. In contrast, solid-state batteries, which are based on solid-state electrolytes, are regarded to have much better safety characteristics and potentially higher energy density than the conventional lithium-ion batteries. Solid-state electrolytes usually include ceramics, polymers, gels, and composites. Among them, polymer materials have attracted considerable attention due to their great interfacial contact, flexibility, and easy fabrication. In particular, polyvinylidene fluoride (PVDF) polymer electrolyte is a promising candidate as it can potentially provide a high voltage window and enable high energy density solid-state batteries. However, the current PVDF-based polymer electrolyte is still not compatible with high voltage cathodes, such as layered lithium transition metal oxides and the interaction between the salt and PVDF polymer has not been fully elucidated.We have systematically studied the PVDF-based electrolytes with different salts and salt combinations, including lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(pentafluoroethanesulfonyl)imide (LiBETI). The optimized electrolyte delivers excellent performance for solid-state Li||LiFePO4 cells, achieving a specific capacity of over 150 mAh/g and lasting more than 50 cycles with over 99% capacity retention. Similar tests have also been applied to lithium nickel manganese cobalt oxides (NMC), and the preliminary results show promising cycling stability and capacity retention. In addition to electrochemical study, we employed a range of synchrotron-based X-ray techniques, including diffraction, pair distribution function analysis, and absorption spectroscopy, to investigate the interactions between the polymer and lithium salt in the polymer electrolytes. This knowledge will provide valuable information for designing new polymer electrolyte systems.Acknowledgments: The work at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program under contract DE-SC0012704. This research used beamline 23-ID-2 and 28-ID-2 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Construction of Polyvinylidene Fluoride Buffer Layers for Li1.3Al0.3Ti1.7(PO4)3 Solid-State Electrolytes toward Stable Dendrite-Free Lithium Metal Batteries

The NASICON-type inorganic electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP) is an ideal solid electrolyte material for solid-state batteries due to its remarkable lithium-ion conductivity, wide electrochemical window, and superb environmental stability. However, its poor contact with electrodes and incompatibility with lithium (Li) anodes cause high interfacial impedance or even electrolyte deactivation. To address these issues, a double-side-modified LATP ceramic pellet with a flexible polyvinylidene fluoride (PVDF) polymer electrolyte capable of promoting LATP/electrode interfacial contact and synchronously modifying LATP/Li interfacial compatibility is constructed. The results demonstrate that the introduction of the PVDF buffer layers effectively reduces the interface impedance (5789 Ω → 271 Ω), prevents the occurrence of unwanted reactions of Li anode and LATP, and thus ensures the stable operation of the battery. The Li/Li cell fabricated by PVDF-modified LATP ceramic pellet exhibits over 3000 h of stable dendrite-free cycling at 0.1 mA cm–2 and small polarization (30 mV). This solid-state LiFePO4/Li battery exhibits a capacity retention of 83.4% after 300 cycles, implying its good cycling stability. This study indicates that such an interfacial modification strategy is effective for anodic protection and contributes to the formation of stable solid-state batteries.

Synthesis of carbon nanofibers from electrospun polyvinylidene fluoride nanofibers for cathode electrodes in Li-O2 batteries

PVDF nanofibers were fabricated by the electrospinning method from polyvinylidene fluoride (PVDF) solutions in mixture of DMF and acetone solvents. PVDF fibers were then converted to CNF fibers through the low-temperature chemical stabilization ("dehydrofluorination") before carbonization at 800°C. The free-standing, perforated features of the CNF-based PVDF enabled the CNF to be directly applied as an air cathode in a LOB just after drying, without requiring additional conducting additives or polymeric binders. The interconnected pores between the individual CNFs were estimated to be 2‒4 µm. This could prevent the electrode from clogging when the discharge product was formed. With the interstitial voids and a large surface area, the CNF electrode synthesized from polymer PVDF had a capacity of 2,600 mAh/g with a current density of 200 mA/g. Moreover, CNF fibers, synthesized from electrospun PVDF nanofibers containing C‒F bonds, could improve the electrode conductivity, forming Li2O2 discharge products with less crystalline properties, leading to overpotential reduction during a discharge. This contributed to the longer cycle life of Li-O2 batteries using the CNF synthesized from electrospun PVDF nanofibers electrode (97 cycles) compared to the one synthesized from electrospun PAN nanofibers electrode (73 cycles) at a limited capacity of 1,000 mA/h and a current density of 200 mA/g. Their structure and morphology were evaluated by Scanning Electron Microscopy, Fourier-transform infrared Spectroscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction, and Raman Spectroscopy.

CNT/PVDF Composite Coating Layer on Cu with a Synergy of Uniform Current Distribution and Stress Releasing for Improving Reversible Li Plating/Stripping.

The uncontrollable formation of polymorphous Li deposits, e.g., whiskers, mosses, or dendrites resulting from nonuniform interfacial current distribution and internal stress release in the upward direction on the conventional current collector (e.g., Cu foil) of Li metal rechargeable batteries with a lithium-metal-free negatrode (LMFRBs), leads to rapid performance degradation or serious safety problems. The 3D carbon nanotubes (CNTs) skeleton has been proven to effectively reduce the current density and eliminate the internal accumulated stress. However, remarkable electrolyte decomposition, inherent Li source consumption due to repeated SEI formation, and Li+ intercalation in CNTs limit the application of 3D CNTs skeleton. Thus, it is necessary to avoid the side effects of the 3D CNTs skeleton and retain uniform interfacial current distribution and stress mitigation. In this work, we integrate the CNTs network with a soft functional polymer polyvinylidene fluoride (PVDF) to form a relatively dense coating layer on Cu foil, which can shield the contact between the internal surface of the 3D CNTs framework and the electrolyte. Simultaneously, the Li-F-rich SEI resulting from the partial reduction of PVDF with deposited Li and the soft nature of the coating layer release the accumulation of internal stress in the horizontal direction, resulting in mosses/whisker-free Li deposition. Thus, improved Li deposition/dissolution and stable cycling performance of the LMFRBs can be achieved.

Sonocatalytic degradation of ciprofloxacin and organic pollutant by 1T/2H phase MoS2 in Polyvinylidene fluoride nanocomposite membrane

The development of recyclable catalysts with effective properties and stable reusability is great importance for the removal of different types of pollutants in wastewater. Herein, we have synthesized Polyvinylidene fluoride (PVDF) polymer and mixed-phase 1T/2H MoS2 for immobilizing the sonocatalyst material. Techniques such as FESEM, XRD, FTIR, XPS, and UV–vis spectra have been used for analyzing the structural, and morphological properties. The formation of a 1T/2H mixed phase in MoS2 has been revealed by XRD and XPS analysis. Consequently, the sonocatalytic performance of the nanocomposite membrane was investigated through ciprofloxacin (CIP) and organic pollutants (Rhodamine B (RhB)). As a result, MoS2/PVDF (PM4) nanocomposite membrane exhibited a superior sonocatalytic activity with 94.37% and 84.37% of RhB and CIP degradation efficiency with pseudo-first-order kinetic constant (k) of 0.0187 min−1, and 0.0044 min−1. The sonocatalytic property of the nanocomposite membrane is related to 1T/2H mixed-phase and PVDF. Additionally, the metallic based 1T phase MoS2 helps to promote electrons and holes and reduce the recombination rate. Moreover, it promotes the generation of more hydroxy radicals (.OH), and superoxide radicals (∙O2−) play a significant role in sonocatalytic degradation of RhB pollutants. Thus, the improved sonocatalytic degradation of 1T/2H MoS2/PVDF composite membrane exhibited its application in real-time wastewater treatment.

Electrospun polyvinylidene fluoride mats as a novel platform for dye-doped random lasing

The development of novel polymer nanofiber-based photonic devices has led to improved optical materials, extremely appealing for random lasers (RLs). Recently, electrospun polymer fibers have been proposed as convenient materials for RLs, leading to a versatile, low-cost strategy for developing new scattering materials. Here we utilize electrospun Polyvinylidene fluoride (PVDF) polymer as the system with randomness (scatterers), varying in all directions, and rhodamine 6 g (R6G) as the gain medium. A transition from amplified spontaneous emission to lasing with coherent feedback in dye-doped electrospun polyvinylidene fluoride polymer mats is observed by increasing the gain concentration from 1 mM to 3 mM. Indeed, for 3 mM dye concentration, we can observe the emergence of sharp laser peaks (where peak width narrows down to ≈ 0.2 nm), which are superimposed on the broad emission band. These results made this simple and powerful disordered platform made of R6G doped electrospun PVDF materials as valuable active media for controllable light emission, which is of paramount importance in optical sensing and for versatile microlaser devices.

Synthesis of One-Dimensional Titanium Oxide Nanowires for Polyvinylidene Fluoride Membrane Optimization

Due to their beneficial characteristics, 1D nanowires have made significant advancements in different realms due to their large surface area, unique surface chemistry, and tunable transport properties. Herein, a comprehensive study of titanium oxide nanowires from titanium (IV) isopropoxide, with the addition of CNTs in the polymeric membrane, has been conducted to form crystals. This method is quite proficient for nanowire synthetization, incorporated with CNTs and polymeric membranes. Carbon nanotubes (CNTs) were used to enhance their properties with polymeric polyvinylidene fluoride PVDF membrane. The concentration ratio of titanium oxide in PVDF membrane was 1, 3, 5, 10, and 15%. The development of titanium oxide nanowires at the nano level shaped, as the emulsion electrospinning created 1D nanowires. The use of an additive makes the membrane more conductive. FT-IR, XRD, EDS, and SEM techniques were used for size, surface geometry, crystalline nature, blend membrane, and thin film composition determination. Thermal Gravimetric Analysis (TGA) analysis shows that weight loss with temperature increases at optimum level.

Investigation on Crystal-Structure, Thermal and Electrical Properties of PVDF Nanocomposites with Cobalt Oxide and Functionalized Multi-Wall-Carbon-Nanotubes.

Nanocomposites of polyvinylidene fluoride (PVDF) with dimensional (1D) cobalt oxide (Co3O4) and f-MWCNTs were prepared successfully by the solution casting method. The impact of 1D Co3O4 filler and 1D Co3O4/f-MWCNTs co-fillers on the structural, thermal, and electrical behavior of PVDF were studied. The crystal structural properties of pure PVDF and its nanocomposite films were studied by XRD, which revealed a significant enhancement of β-phase PVDF in the resulting nanocomposite films. The increase in β-phase was further revealed by the FTIR spectroscopic analysis of the samples. TG, DTA, and DSC analyses confirmed an increase in thermal stability of PVDF with the addition of nano-fillers as well as their increasing wt.%. From impedance spectroscopic studies, it was found that the DC conductivity of PVDF increases insignificantly initially (up to 0.1 wt.% of nano-fillers addition), but a significant improvement in DC conductivity was found at higher concentrations of the nano-fillers. Furthermore, it was observed that the DC conductivity decreases with frequency. The increase in DC conductivity corresponded to the strong interactions of nano-fillers with PVDF polymer chains.

Study on Filtration Performance of PVDF/PUL Composite Air Filtration Membrane Based on Far-Field Electrospinning.

At present, the situation of air pollution is still serious, and research on air filtration is still crucial. For the nanofiber air filtration membrane, the diameter, porosity, tensile strength, and hydrophilicity of the nanofiber will affect the filtration performance and stability. In this paper, based on the far-field electrospinning process and the performance effect mechanism of the stacked structure fiber membrane, nanofiber membrane was prepared by selecting the environmental protection, degradable and pollution-free natural polysaccharide biopolymer pullulan, and polyvinylidene fluoride polymer with strong hydrophobicity and high impact strength. By combining two kinds of fiber membranes with different fiber diameter and porosity, a three-layer composite nanofiber membrane with better hydrophobicity, higher tensile strength, smaller fiber diameter, and better filtration performance was prepared. Performance characterization showed that this three-layer composite nanofiber membrane had excellent air permeability and filtration efficiency, and the filtration efficiency of particles above PM 2.5 reached 99.9%. This study also provides important reference values for the preparation of high-efficiency composite nanofiber filtration membrane.

Investigation of different molecular weight Polyvinylidene Fluoride (PVDF) polymer for the fabrication and performance of braid hollow fiber membranes

ABSTRACT In the current study, braid reinforced membranes were fabricated from polyvinylidene fluoride (PVDF) polymers with two different molecular weights, and the blending of the polymers in a 1:1 ratio to upgrade the performance of the membrane. Characterization, filtration studies, and membrane bioreactor (MBR) application were done to evaluate membrane performance by applying the same operation conditions on each membrane. Characterization studies indicated that the fabricated membrane from blending polymers was a hydrophilic structure with a contact angle of 50.78° and smoother surface properties compared to the other fabricated membranes. According to the MBR results, at the end of the operation process, TMP levels of the membrane from the blending method are found 150 mbar, membrane from high molecular weight PVDF polymer had 250 mbar, and membrane from low molecular weight PVDF polymer had 800 mbar. As a consequence of the investigation, it is seen that the hydrophilic structure of the membrane allows the pollutant to adsorb less to the blend membrane surface, and the lower roughness is also a factor in reducing fouling.

Characteristics of a PVDF-Tin Dioxide Membrane Assisted by Electric Field Treatment.

Polymeric membranes have good properties for filtering water. In this paper, a membrane made from polyvinylidene fluoride (PVDF) polymer with 15 wt%, 17.5 wt%, and 20 wt% polymer content, with the addition of 1 wt% of tin dioxide with electric field treatment, is presented. The electric field used was DC 15,000 V. The membrane was tested to determine its characteristics and properties. The physical properties were examined with a scanning electron microscope, and the mechanical properties of the membrane were tested by tensile testing. The maximum tensile stress was obtained at 0.746 MPa, and the minimum tensile stress was obtained at 0.487 MPa. Microscopic examination of the membrane’s surface identified the shape, the structure of the fibers formed, and the amount of agglomeration. The flow rate, membrane flux, and normalized water permeability (NWP) were tested, using the water treatment performance test to measure the membrane’s filtering ability.

Electrochemical Aging and Characterization of Graphite-Polymer Based Composite Bipolar Plates for Vanadium Redox Flow Batteries

Three bipolar plates (BPP) comprised of a composite of polypropylene or polyvinylidene fluoride polymer and varying average graphite particle size were studied for application in a vanadium redox flow battery (VRFB). The BPPs were electrochemically aged via 3000 cyclic voltammetry curves in 1.8 M VOSO4 + 2.0 M H2SO4 electrolyte. After every 500th cycle the aging progression was determined by performing cyclic voltammetry on the bipolar plates in 0.1 M H2SO4 solution where the double layer capacitance, the quinone/hydroquinone and the vanadium species redox activity were quantitatively evaluated. Prior to the aging, the composite plates were extensively characterized using various physical methods. The performed studies reveal that the wettability, surface roughness and accessible porosity of the bipolar plates significantly influence their electrochemical stability. Cycling tests in vanadium redox flow single cells at a constant current density of 60 mA cm−2 revealed a close correlation of the cell efficiencies to the electrochemical stability of the bipolar plates. Thus, the proposed electrochemical characterization method can be an effective foresight to predict the applicability of a bipolar plate in a vanadium redox flow battery.

Towards an interpretable machine learning model for electrospun polyvinylidene fluoride (PVDF) fiber properties

A robust understanding of structure–property relations of electrospun fibers is vital for device design. However, these relationships are inherently complex and hard to model using data from limited trial and error experiments. Machine learning has emerged as an efficient approach to model multidimensional relationships but fundamentally require diverse data to learn these relationships from. In this study, we present a novel Electrospun Fiber Experimental Attributes Dataset (FEAD) by collating experimental data from literature, developing new features, and complementing with our own experiments. Fiber diameter, a key parameter for controlling electrical and thermal properties of electrospun polyvinylidene fluoride (PVDF) polymer, is modeled using a large number of solution and electrospinning process experimental parameters using a multi-model machine learning approach. This is complemented with a model-agnostic interpretable game-theoretic approach to identify the relative and absolute relationships between the variables. Experimental attributes such as feed, polymer concentration, Flory-Huggins Chi parameter, and relative energy difference were found to be most impactful for modeling fiber diameter. This study overcomes several limitations in existing literature such as non-availability of meta datasets, application of latest machine learning techniques, and state-of-the-art approaches for interpreting these “black box” models, thus bridging the gap between experimental and computational studies. This improved ability to generalize structure–property relationships across any PVDF-polymer solvent system presents a promising ability to reduce expensive lab testing required for developing PVDF fibers of desired mechanical and electrical properties.

Rapid Forming of Nanowire Array on Polyvinylidene Fluoride Polymer Surfaces at Room Temperature by Ultrasonic Loading

Forming nanostructures on a substrate have been an effective approach to regulating surface properties without changing material chemical compositions. However, such nano‐forming processes are generally based on thermal plastic forming that needs to heat substrate material to its melting point, which is time‐consuming and induces a risk of oxidation, aging, or phase transition, especially when the material is a polymer. This research work develops a novel method to rapidly form nanowire arrays on polyvinylidene fluoride (PVDF) polymer at room temperature. Assisted by ultrasonic vibration, nanowires with a diameter of 200 nm are formed on PVDF surface within 0.7 s, while the highest forming temperature is 124 °C only, which is much lower than the melting point. In addition, the original β phase of PVDF can be retained after nano‐forming by adjusting ultrasonic loading time. The agglomeration mechanism of the formed nanowires on the surface was also proposed based on the transverse flow and residual stress release during ultrasonic forming process. The water contact angle measurement showed that nanowire arrays altered the surface wettability of PVDF from hydrophilic to hydrophobic. This ultrasonic‐assisted processing provides a new approach for functional surface design of PVDF and rapid nanostructure forming for various applications.

Effect of TiO2 Nanoparticles on Capillary-Driven Flow in Water Nanofilters Based on Chitosan Cellulose and Polyvinylidene Fluoride Nanocomposites: A Theoretical Study.

In this study, a novel concept of nanofiltration process of drinking water based on capillary-driven nanofiltration is demonstrated using a bio-based nanocomposites’ nanofilter as free power: a green and sustainable solution. Based on Lifshitz and Young–Laplace theories, we show that the chitosan (CS), cellulose acetate (CLA), and Polyvinylidene fluoride (PVDF) polymer matrixes demonstrate hydrophobic behavior, which leads to the draining of water from nanopores when negative capillary pressure is applied and consequently prevents the capillary-driven nanofiltration process. By incorporating 10%, 20%, and 30% volume fraction of titanium dioxide (TiO2) nanoparticles (NPs) to the polymers’ matrixes, we demonstrate a wetting conversion from hydrophobic to hydrophilic behavior of these polymer nanocomposites. Subsequently, the threshold volume fraction of the TiO2 NPs for the conversion from draining (hydrophobic) to filling (hydrophilic) by capillary pressure were found to be equal to 5.1%, 10.9%, and 13.9%, respectively, for CS/TiO2, CLA/TiO2, and PVDF/TiO2 nanocomposites. Then, we demonstrated the negligible effect of the gravity force on capillary rise as well as the capillary-driven flow for nanoscale pore size. For nanofilters with the same effective nanopore radius, porosity, pore shape factor, and tortuosity, results from the modified Lucas–Washburn model show that the capillary rise as well as the capillary-driven water volume increase with increased volume fraction of the TiO2 NPs for all nanocomposite nanofilter. Interestingly, the capillary-driven water volume was in range (5.26–6.39) L/h·m2 with 30% volume fraction of TiO2 NPs, which support our idea for capillary-driven nanofiltration as zero energy consumption nano-filtration process. Correspondingly, the biodegradable CS/TiO2 and CLA/TiO2 nanocomposites nanofilter demonstrate capillary-driven water volume higher, ~1.5 and ~1.2 times, respectively, more than the synthetic PVDF/TiO2 nanocomposite.

Exploring the Interplay between Composite Cathode Design and Cell Performance for Solid-State Lithium Batteries

To accelerate the mass market adaptation of electric vehicles (EVs), raising the gravimetric energy density of batteries to > 250 Wh/kg while maintaining a cost target of < $ 120/kWh is of critical importance (the ultimate targets of the U.S. Department and the advanced battery consortium).[1] Solid-state batteries are widely recognized as excellent prospects for application in the next generation of EVs and other energy storage devices, with the promise to realize higher energy densities, superior safety and environmentally friendly characteristics. At the cell level, the development of SSBs has been hampered by challenges with the interface originating from the poor interfacial stability between the solid-state electrolytes (SSE) and the electrodes. By eliminating the liquid electrolyte, conductive pathways throughout the whole thickness of the positive electrode and at the solid-solid interface become less efficient causing large polarization and diminished cell performance. This can be exacerbated by the current urge to use thicker electrodes in an attempt to increase the energy density which is a common practice in the currently widely adapted lithium ion batteries employing liquid electrolytes. Notably, increasing cathode thickness beyond a certain limit leads to a point of diminishing returns in terms of energy density. This is mainly attributed to the dominating effect of porosity at higher cathode thickness.[2,3] For instance, it has been found that cells with NMC cathodes thinner than 155 μm (< 6.5 mAh cm-2) showed excellent cycling stability and no capacity losses for C-rates up to 0.5C.[4] To address this challenge, one approach is to formulate the cathode (positive electrode) using a small fraction of ionic conductors (Catholyte) that are mostly derived from the solid electrolyte formulation. In addition, this approach could be complemented with the application of a 10 μm intermediate SSE coating at the cathode surface. The use of catholytes has a second advantage of replacing the non-green polymer polyvinylidene fluoride (PVDF) which is currently the most commonly used binder. Having fluorine in its structure, PVDF is non-recyclable and a potential source of environmentally harmful fluorocarbons.[5] We have begun studying the interfacial stability between composite cathodes using LiFePO4 (LFP), a safe, environmentally-friendly, 3.4 V cathode material, and different SSEs including ceramic electrolytes, polymer electrolytes and polymer-ceramic composite electrolytes. In this work, an optimally designed DOE was planned to study the impact of varying active material mass loading in composite cathodes, and the significance of intermediate coating on SSB electrochemical performance. The SSE used is a plasticized polymer electrolyte with the following optimized formula: 77 % PEO, 13% LiTFSI and 10% Succinonitrile (SN) while the composite cathode was composed of 86% LFP, 4% C65 conductive carbon and 10% of the aforementioned SSE as the catholyte. The active material mass loading was varied between 1 – 12 mg cm-2 in 1 mg cm-2 increments and all composite cathodes were tested with and without the intermediate coating layer. This powerful and contemporary statistical approach aims to provide an enhanced design strategy for a popular and very promising SSB chemistry (Li/PEO/LFP). Finally, our findings shed light on a new approach that can be adopted to explore other battery chemistry with higher voltages such as oxide cathodes, non-oxide solid or semi-solid electrolytes.

Na Plating and Stripping Using Highly Na-Ion Conductive Solid Polymer Electrolytes Based on Polyvinylidene Fluoride and Polyvinylpyrrolidone

Solid-state sodium-ion batteries (ss-SIBs) are a promising alternative to commercially available lithium-ion batteries (LIBs) for next-generation energy storage applications. They have lower production costs and are safer than LIBs. Moreover, sodium is more abundant than lithium. The incorporation of solid polymer electrolytes (SPEs) into SIBs has been attracting much more attention due to the easy processability, low costs, safe usability, modification scope, and abundance of polymers. However, SPEs for ss-SIBs with high ionic conductivity and low interfacial resistance between electrolytes and electrodes are lacking. In addition, SPEs face major challenges such as suitable manufacturing methods and the lack of knowledge about low-cost ss-SIBs assembly. Herein, using a facile solution casting process, we have successfully fabricated a high sodium-ion conductive composite SPE film based on polyvinylidene fluoride (PVDF) polymer, polyvinylpyrrolidone (PVP) binder, and NaPF6 salt. A comprehensive characterization has been conducted using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Thermogravimetric Analysis (TGA), Raman, and electrochemical impedance spectroscopy techniques to investigate the structural, thermal, and electrochemical performance of the as-prepared SPE films. High ionic conductivity (8.51 x 10-4 S cm-1 and 8.36 x 10-3 S cm-1 at 23°C and 78 °C, respectively) was observed from the SPE. A hybrid symmetric half-cell assembly (Na foil + 20 µL of 1 M NaClO4 in ethylene carbonate (EC) and propylene carbonate (PC) (EC: PC = 1:1) + Carbon-cloth |SPE| Carbon-cloth + 20 µL of 1 M NaClO4 in EC and PC (EC: PC = 1:1) | Na foil) showed excellent Na plating-stripping performance up to 8 mA cm-2 for 100 cycles. In addition, Na+ transfer mechanism in the composite electrolyte has been investigated using impedance and dielectric spectroscopy. The results indicate the promising applicability of SPEs in next-generation high-power rechargeable SIBs.

Impact of Polymers on Magnesium-Based Hydrogen Storage Systems

In the present scenario, much importance has been provided to hydrogen energy systems (HES) in the energy sector because of their clean and green behavior during utilization. The developments of novel techniques and materials have focused on overcoming the practical difficulties in the HES (production, storage and utilization). Comparatively, considerable attention needs to be provided in the hydrogen storage systems (HSS) because of physical-based storage (compressed gas, cold/cryo compressed and liquid) issues such as low gravimetric/volumetric density, storage conditions/parameters and safety. In material-based HSS, a high amount of hydrogen can be effectively stored in materials via physical or chemical bonds. In different hydride materials, Mg-based hydrides (Mg–H) showed considerable benefits such as low density, hydrogen uptake and reversibility. However, the inferior sorption kinetics and severe oxidation/contamination at exposure to air limit its benefits. There are numerous kinds of efforts, like the inclusion of catalysts that have been made for Mg–H to alter the thermodynamic-related issues. Still, those efforts do not overcome the oxidation/contamination-related issues. The developments of Mg–H encapsulated by gas-selective polymers can effectively and positively influence hydrogen sorption kinetics and prevent the Mg–H from contaminating (air and moisture). In this review, the impact of different polymers (carboxymethyl cellulose, polystyrene, polyimide, polypyrrole, polyvinylpyrrolidone, polyvinylidene fluoride, polymethylpentene, and poly(methyl methacrylate)) with Mg–H systems has been systematically reviewed. In polymer-encapsulated Mg–H, the polymers act as a barrier for the reaction between Mg–H and O2/H2O, selectively allowing the H2 gas and preventing the aggregation of hydride nanoparticles. Thus, the H2 uptake amount and sorption kinetics improved considerably in Mg–H.

Enhancing the properties of PVDF/MFe2O4; (M: Co–Zn and Cu–Zn) nanocomposite for the piezoelectric optronic applications

Polyvinylidene fluoride (PVDF) polymer is considered as an encouraging piezoelectric material whose optical properties need to be enhanced. Zinc ferrite is an excellent photoelectric material, in the present work it was doped separately by (cobalt and copper) ferrite. Co-ZnFe2O4 and Cu-ZnFe2O4 nanoparticles were synthesized using auto-combustion method and characterized using XRD, FTIR, FESEM and HRTEM. The crystallite size was (28.8, 35.8, 22 and 31) nm for the Co-ZnFe2O4 and Cu-ZnFe2O4 nanoparticles, while the estimated particle size from HRTEM were 55 nm for the Co-ZnFe2O4 nanoparticles and 75 nm for the Cu-ZnFe2O4. The obtained samples used as PVDF fillers, aiming to improve its optical properties. The optical properties as well as, the piezoelectric response of the prepared PVDF/(Co-ZnFe2O4 and Cu-ZnFe2O4) nanocomposites were investigated. The maximum value for refractive index was related to PVDF/Co-ZnFe2O4 nanocomposite. While, Cu-ZnFe2O4 nanoparticles have limited improvement of the PVDF optical properties. Co-ZnFe2O4 nanoparticles increases the PVDF optical conductivity σopt. four times its original value as well as the dielectric values was increased from 0.05 for neat PVDF to 2. The piezoelectric response of the PVDF polymer is clearly increased by the addition of both Co-ZnFe2O4 and Cu-ZnFe2O4 nanoparticles.