Polyvinylidene Fluoride Nanofiber Membrane Research Articles

All-Textile Piezoelectric Nanogenerator Based on 3D Knitted Fabric Electrode for Wearable Applications.

Flexible, air permeable and elastic self-powered sensors for human motion monitoring and assisted medical rehabilitation have recently become a hot research topic. However, most current piezoelectric sensors can not account for many characteristics. Addressing this challenge, an all-textile piezoelectric sensor (ATPS) based on 3D structured knitted fabric electrodes is reported. The ATPS consists of a piezoelectric element polyvinylidene fluoride nanofiber membrane, flexible knitted fabric electrodes, and an elastic self-adhesive bandage. Based on the flexible and efficient knitting technology, the sensor has the advantages of low cost, flexibility, simple structure, and convenient large-area manufacturing. Experimental and finite element simulation results show that the knitting pattern of fabric electrodes can enhance the piezoelectric output of ATPS. The optimal ATPS has a high voltage response sensitivity of up to 0.68 V/kPa. The proposed ATPS responds to a wide range of input forces from 0.098 to 724 N in self-powered mode, verifying its feasibility as a tactile sensor for human motion detection and recognition (throat swallowing, wrist bending, elbow bending, knee bending, walking slowly, running fast) and as a pressure sensor (Morse code, digit recognition) and demonstrating its potential for motion tracking, medical rehabilitation, and human-computer interaction.

Contact-electro-catalysis for degradation of trace antibiotics in wastewater

Antibiotic contamination of water bodies is a major concern in environmental management. Despite their superior efficacy in antibiotic removal, advanced oxidation processes (AOPs) have yet to be widely adopted owing to their substantial cost associated with the large amounts of chemicals required. In this study, a novel contact-electro-catalysis (CEC) process with reusable polytetrafluoroethylene (PTFE) particles as a trigger catalyst was applied to replace traditional AOPs, and it was able to degrade three typical antibiotics (sulfamethoxazole [SMX], ciprofloxacin [CIP], and tetracycline [TET]) in the secondary effluent of a wastewater treatment plant for the first time. The PTFE particles at a concentration of 0.8 g/L were introduced into antibiotic solutions with an antibiotic concentration of 1 mg/L, and the removal rates of SMX, CIP, and TET after a 90-min operation time reached 50 %, 80 %, and 90 %, respectively. Our findings revealed that the CEC reaction generated ●OH and 1O2, contributing substantially to antibiotic degradation. Thus, new reactive oxygen species generation mechanisms during the CEC process were proposed. Furthermore, we fabricated polyvinylidene fluoride nanofiber membranes using electrospinning to recycle PTFE particles, where a nearly 100 % recovery rate through dead-end filtration was realized with a high water flux of 7.5 m3/(m2∙h). The results of this study provide a promising approach for antibiotic removal from wastewater.

Durable and comfortable electrospun nanofiber membranes for face mask applications

Airborne contaminants, including particulate matters (PM), pathogens, and gases are presenting serious health challenges. Electrospinning has emerged as a facile technique for synthesizing nanofiber membranes to be used to separate airborne contaminants. Herein, nanofiber membranes were formed from polyvinylidene fluoride (PVDF) by systematic optimization of the electrospinning process to generate highly efficient face masks. A scalable and comfort (low pressure drop) PVDF nanofiber membrane with high filtration efficiency was achieved through controlling operation parameters of electrospinning process, allowing for controlled inter-fiber spacing and fiber density, and enhanced air filtration performance, durability and comfort of wearing. The PVDF nanofiber membranes exhibited smaller fiber diameter and higher mechanical strength as compared with commercial surgical face masks. The PVDF nanofiber membranes also revealed air filtration efficiencies in the range of 95.8 to 99.7 % for the most penetration particle size (MPPS) 300 nm based on basis weight, higher than commercial surgical mask and the respiratory filter media standards. The quality factor (QF) of PVDF nanofiber membranes is double that of the commercial surgical mask. The PVDF membranes also yielded excellent water vapour transmission (WVT), water contact angle up to 138.6˚, thus supporting the designing of durable and washable membranes. This strategy opens opportunities to be used as environmentally friendly reusable face masks for the removal of ultrafine airborne contaminants, including PM, toxic gases, and pathogens.

Research of different needle length on properties of PVDF nanofiber membrane based on long-needle electrospinning technology

In this paper, we combine electrospinning with laminar flow theory to verify the influence of the spinning needle length on the internal structure of PVDF (polyvinylidene fluoride) nanofibers. The long spinning needle is referred as a reference like long ducts in the body of spiders. We also discussed the effect of different needle length on the micro-morphology, mechanical properties, electrical properties, porosity, and hydrophobic properties of PVDF nanofiber membranes. The results showed that when the needle length increased, more PVDF macromolecular chains will have sufficient time to be straightened and aligned, resulting in an increasingly ordered internal structure of the prepared PVDF nanofibers. The different length of the long needle has a certain influence on the morphology, mechanical properties, electrical properties, porosity, and hydrophobic properties of PVDF nanofiber membrane obtained by electrospinning. The more ordered the internal structure of nanofibers, the worse the membrane’s mechanical properties, but the lower its electrical resistivity.

Lotus leaf-like SiO2 nanofiber coating on polyvinylidene fluoride nanofiber membrane for water-in-oil emulsion separation and antifouling enhancement

Separation of water-in-oil emulsions is necessary to recycle valuable resources in practical industries, as well as to protect the natural environment from damage. However, the formation of a filter cake layer by tiny water droplets, which commonly sticks to the membrane surface and is difficult to remove, limits the efficiency of the separation process. Therefore, an enhancement in the antifouling property is required to relieve the impact of the high cost and energy consumption caused by fouling. The construction of a hierarchical surface is a promising strategy, but extant coating methods have shortcomings that inhibit their widespread application and scalability. We report a sprayable premodified SiO2 nanofiber coating, which has a lotus leaf-like hierarchical surface, interconnected porous network, and superwetting properties, on a polyvinylidene fluoride nanofiber membrane to mitigate the fouling. The resultant membrane with the biomimetic coating exhibited a completely recovered flux in the recycling test while the pristine membrane exhibited an irreversible flux. Owing to this favorable reusability, this biomimetic coating membrane is a promising platform for an industrial water-in-oil emulsion separation.

Facile self-assembly-based fabrication of a polyvinylidene fluoride nanofiber membrane with immobilized titanium dioxide nanoparticles for dye wastewater treatment

Photocatalytic membrane technology has received significant research attention because this system can continuously and safely purify wastewater without the post-process of separating and recovering the nanoscale photocatalysts. However, conventional membrane technology cannot wholly derive the photocatalytic performance due to the limitation in the loading contents of nanoscale photocatalyst and the reduced reactive sites. In this study, in order to overcome these issues and the limitations of current fabrication methods for photocatalytic membranes, a versatile and facile self-assembly approach for a polyvinylidene fluoride (PVDF) fiber-based reusable photocatalytic membrane with immobilized titanium dioxide (TiO2) nanoparticles is demonstrated to maximize the loading contents and photocatalytic reaction sites of nanoparticles on the surface of polymeric membrane. The TiO2 nanoparticles were successfully immobilized in high loading content on the surface of electrospun PVDF fibers using a poly(styrene-alt-maleic anhydride) as a self-assembly reaction agent at room temperature. Then, the physicochemical properties of the fabricated photocatalytic membrane and the manufacturing mechanism are systematically characterized. The photocatalytic properties of the membrane according to the loading of immobilized TiO2 nanoparticles are evaluated based on the degradation of various dye solutions under the illumination of a Xenon lamp (incident light intensity = 100 mW/cm2). The photocatalytic performance of the membrane is considerably enhanced when the loading of immobilized TiO2 nanoparticles on the PVDF fibers is higher as a result of a more vigorous self-assembly reaction. Furthermore, the reusability of the membrane is evaluated by repeating the dye removal process via adsorption and light irradiation; after the 20th cycle, it is demonstrated that the dye removal efficiency remains high without any leakage of TiO2 nanoparticles. The proposed facile fabrication method for a photocatalytic membrane with excellent reusability thus offers a new approach for the design of industrially applicable high-efficiency photocatalytic membranes.

Ferroelectric PVDF nanofiber membrane for high-efficiency PM0.3 air filtration with low air flow resistance

The significant public health concerns related to particulate matter (PM) air pollutants and the airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have led to considerable interest in high-performance air filtration membranes. Highly ferroelectric polyvinylidene fluoride (PVDF) nanofiber (NF) filter membranes are successfully fabricated via electrospinning for high-performance low-cost air filtration. Spectroscopic and ferro-/piezoelectric analyses of PVDF NF show that a thinner PVDF NF typically forms a ferroelectric β phase with a confinement effect. A 70-nm PVDF NF membrane exhibits the highest fraction of β phase (87%) and the largest polarization behavior from piezoresponse force microscopy. An ultrathin 70-nm PVDF NF membrane exhibits a high PM0.3 filtration efficiency of 97.40% with a low pressure drop of 51 Pa at an air flow of 5.3 cm/s owing to the synergetic combination of the slip effect and ferroelectric dipole interaction. Additionally, the 70-nm PVDF NF membrane shows excellent thermal and chemical stabilities with negligible filtration performance degradation (air filtration efficiency of 95.99% and 87.90% and pressure drop of 55 and 65 Pa, respectively) after 24 h of heating at 120 °C and 1 h immersion in isopropanol.

Fabrication and Characterization of Nanofibers Membranes using Electrospinning Technology for Oil Removal

Oily wastewater is one of the most challenging streams to deal with especially if the oil exists in emulsified form. In this study, electrospinning method was used to prepare nanofiberous polyvinylidene fluoride (PVDF) membranes and study their performance in oil removal. Graphene particles were embedded in the electrospun PVDF membrane to enhance the efficiency of the membranes. The prepared membranes were characterized using a scanning electron microscopy (SEM) to verify the graphene stabilization on the surface of the membrane homogeneously; while FTIR was used to detect the functional groups on the membrane surface. The membrane wettability was assessed by measuring the contact angle. The PVDF and PVDF / Graphene membranes efficiency was tested in separation of emulsified oil from aqueous solutions. The results showed that PVDF-Graphene nanofiber membrane exhibited better performance than the plain PVDF nanofiber membrane with average water flux of 210 and 180 L.m-2.h-1, respectively. Both membranes showed high oil rejection with more than 98%.

Ultrafine PVDF Nanofibers for Filtration of Air-Borne Particulate Matters: A Comprehensive Review.

The ongoing global pandemic has bestowed high priority uponthe separation of air-borne particulate matters (PMs), aerosols, etc. using nonwoven fibrous materials, especially for face masks as a means of personal protection. Although spunbond or meltblown nonwoven materials are amongst the forerunners for polymer microfiber-based face mask or air filter development in mass scale, relatively new process of nonwoven manufacturing such as electrospinning is gaining a lot of momentum amongst the filter membrane manufacturers for its scalability of nanofiber-based filter membrane fabrication. There are several nanofiber-based face masks developing industries, which claim a very high efficiency in filtration of particulate matters (PM0.1–10) as well as other aerosols for their products. Polyvinylidene fluoride (PVDF), which is commonly known for its use of tactile sensors and energy harvesters, due to its piezoelectric property, is slowly gaining popularity among researchers and developers as an air filter material. Electrospun PVDF nanofibers can be as fine as 50 nm in mass scale, which allows the membrane to have large surface area compared to its volume, enhancing nanofiber–PM interaction. At the same time, the breathability index can be improved through these PVDF nanofiber membranes due to their architectural uniqueness that promotes slip flow around the fibers. The conductive nature of PVDF makes it advantageous as a promising electret filter allowing better capturing of ultrafine particles. This review aims to provide a comprehensive overview of such PVDF nanofiber-based filter membranes and their roles in air filtration, especially its application in filtrate of air-borne PMs.

Removal of cadmium ions from water using coaxially electrospun PAN/ZnO-encapsulated PVDF nanofiber membranes

Electrospun nanofiber membranes have been widely used as heavy metal ion adsorbents. However, they are usually mechanically weak, which reduces the chances of employing such materials in environments that involve stresses and strains. In this work, core–shell nanofiber membranes were directly produced by coaxial electrospinning of polyvinylidene fluoride (PVDF) nanofibers as core nanofibers to provide mechanical support, and zinc oxide (ZnO) nanoparticles loaded PAN as shell nanofibers to enhance the adsorption of cadmium ions. The effect of pH, time and concentration on the adsorption properties was investigated. The incorporation of ZnO nanoparticles to the membrane matrix led to a significant enhancement of 75% in adsorption capacity compared to the membrane without ZnO nanoparticles (i.e., 350 mg/g for PVDF-PAN/ZnO compared to 200 mg/g for PVDF-PAN). The nonlinear optimization method showed that the experimental results are better fitted with the pseudo-second-order kinetic model and Langmuir isotherm equation. In addition, the tensile breaking strength values for PAN, PVDF, PVDF-PAN and PVDF-PAN/ZnO nanofiber membranes were 1.3 ± 0.3, 8.2 ± 0.3, 8.4 ± 0.1 and 3.1 ± 0.3 MPa, respectively, which suggests the enhancement of mechanical properties with the addition of PVDF as core nanofibers.

Fabrication and characterization of polyvinylidene fluoride nanofibers prepared by electrospinning technique

Electrospinning is a technique that produces polymer fibers with diameters in the submicron range. In this study, some electrospinning parameters affecting the morphology, average diameter, and distribution of the diameter of polyvinylidene fluoride (PVDF) fibers were investigated by using scanning electron microscopy (SEM). These electrospinning parameters include solution concentration, applied voltage, the feed rate of solution, distance from the needle to the collector, and solvent mixture. PVDF fibers have a fine structure, narrow distribution of fiber diameter, and average fiber diameter of 736 nm at a solution concentration of 20 wt%, solvent mixture with 60/40 weight of N,N-dimethylacetamide (DMAc) and acetone (Ac), an applied voltage of 11 kV, the feed rate of 1 ml/h, and the distance from the needle to the collector of 17 cm. The hydrophobic property and tensile strength of the PVDF nanofiber membrane were also reported. PVDF nanofibers have the potential to apply in several areas such as water or gas filtration, catalyst, lithium battery, ect.

Development of tree-like nanofibrous air filter with durable antibacterial property

High filtration performance and antibacterial property have been the main concerns of air filters. In this work, the silver nanoparticles (AgNPs) were produced by liquid phase reduction method and were added into polyvinylidene fluoride (PVDF) solutions at a ratio of 0.2%, 0.4%, 0.6%, 0.8%, and 1% for electrospinning. Nanofibers with the tree-like structure were fabricated by controlling the processing parameters. Therefore, a tree-like AgNPs/PVDF nanofiber membrane containing AgNPs was successfully developed. The AgNPs solutions were analyzed by UV–vis absorption spectrum to determine the size of AgNPs, and the nanofiber membranes were also evaluated in terms of morphology, structure, hydrophobic property, filtration performance, and antibacterial property. The results showed that the size of AgNPs was approximately 10 nm, the average diameters of branch-like fibers and stem-like fibers were about 30.8 nm and between 90 nm with 140 nm, respectively. The addition of AgNPs did not change the hydrophobic property of the PVDF nanofiber membrane; the filtration efficiency of AgNPs/PVDF nanofiber membrane was 99.95–99.97% and the lowest pressure drop was 137.5 Pa; the bacterial reduction rates (BR) value against for S. aureus and E. coli were kept at a level of higher than 99.6% after exposure to sunlight for two weeks. Therefore, a kind of air filter with high filtration performance and durable antibacterial property was successfully developed by adding AgNPs and by creating tree-like structure fibers.

Polyvinylidene fluoride nanofibers with embedded Li6.4La3Zr1.4Ta0.6O12 fillers modified polymer electrolytes for high-capacity and long-life all-solid-state lithium metal batteries

Solid polymer electrolytes replacing traditional liquid electrolytes are considered as an important strategy for developing lithium metal batteries with high safety and energy density. However, poor ionic conductivity and weak mechanical performances have greatly limited the development of solid polymer electrolytes. Here, we dispersed inorganic ceramic particles Li6·4La3Zr1·4Ta0·6O12 (LLZTO) in the polyvinylidene fluoride (PVDF) electrospun nanofibers and then introduced them into polyethylene oxide (PEO) polymers to prepare composite electrolytes. The PVDF nanofibers with embedded LLZTO fillers can simultaneously reduce the crystallinity of the PEO polymer and provide a strong framework support for the composite electrolyte, thereby promoting the transmission of lithium ions and improving the lithium dendrite growth inhibition ability of the composite electrolyte. In addition, the uniform dispersion of garnet-type LLZTO active ceramic filler in the PVDF nanofiber membrane can further optimize the migration path of lithium ions. More importantly, the dehydrofluorination of PVDF due to the introduction of LLZTO can enhance the interaction among PVDF, LLZTO and lithium salts, which promotes dissociation of the lithium salt. The ionic conductivity of the composite electrolyte is as high as 9.30 × 10−4 S cm−1 at 50 °C, and the voltage of Li/Li symmetrical battery would not change significantly during 1200 h at 0.3 mA cm−2. Additionally, the composite electrolytes exhibit good electrochemical stability with the capacity retention rate of 96% under 1 C after 500 cycles. These results provide a strategy for the development of next-generation high-safety all-solid-state lithium metal batteries.

Sandwich-like sound-driven triboelectric nanogenerator for energy harvesting and electrochromic based on Cu foam

As a kind of environmental dissipative energy, acoustic energy is common but difficult to collect and utilize effectively owing to its low energy density and special acoustic state. In this work, a new type of triboelectric nanogenerator (TENG) based on porous foam copper with sandwich-like friction pairs is designed to harvest sound energy efficiently from the environment. The sound-driven TENG is mainly composed of Cu foam, polyvinylidene fluoride (PVDF) nanofibers and nylon fabric, in which the Cu foam is used as a sound collector, conductor and amplifier, as well as the friction layer and conductive layer of the TENG. The thin and light PVDF nanofiber membrane and nylon fabric are used as vibration membranes, which are easy to generate vibration under weak sound to harvest the sound energy under wideband frequencies. This sound-driven TENG shows high triboelectric output performance with a maximum current density up to 25.01 mA/m2 and a charging rate of 20.91 μC/s with a charging transformation efficiency up to 59.85%, which can light up 384 LEDs and drive an electrochromic device for reversible color changing. Importantly, the sound-driven TENG has good working stability. It can work continuously for 7 days under loudspeaker driving without decay. This type of sound-driven TENG has potential application in the field of audio frequency analysis, noise detection, energy supply and presents promising potential to be a self-powered system in the electrochemical industry.

A flexible capacitive sensor based on the electrospun PVDF nanofiber membrane with carbon nanotubes

Flexible pressure sensors have been increasingly recognized over the past several decades, but there is still a challenge to fabricate them with a superb sensitivity and large sensing range. In this paper, a flexible capacitive pressure sensor based on the electrospun polyvinylidene fluoride (PVDF) nanofiber membrane with carbon nanotubes (CNTs) was developed to measure the pressure. The electrospinning CNT-PVDF nanofiber membrane can overcomes the limitations of the traditional solution-dip-coating for adhering conductive materials to the porous surface. The microstructure and characterization of the CNT-PVDF nanofiber membrane were analyzed by SEM, AFM and FTIR. By increasing the permittivity and decreasing the Young's modulus of the CNT-PVDF dielectric layer, the capacitive sensor exhibits high sensitivity (∼0.99/kPa), fast response (∼29 ms) and excellent cyclic loading/unloading stability (＞1000 cycles). Moreover, experiments were also conducted to investigate influence of the thickness and bending radius of the sensor as well as temperature and humidity of the environment. In addition, a 3 × 3 sensor network attached on the hand was used to measure the spatial distribution and magnitude of tactile pressure. The proposed sensor has great potential for application in soft robotics and electronic skin.

Novel Quasi-Solid-State Electrolytes based on Electrospun Poly(vinylidene fluoride) Fiber Membranes for Highly Efficient and Stable Dye-Sensitized Solar Cells

To obtain new highly efficient and stable quasi-solid dye-sensitized solar cells (QS-DSSCs) that can meet the requirements for the large-scale commercial application of solar cells, we have developed a novel quasi-solid-state electrolyte, based on an electrospun polyvinylidene fluoride (PVDF) membrane. The structure and properties of electrospun PVDF membranes were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), thermogravimetric (TG), and mechanical testing. The results indicate that the electrospun PVDF membrane has a three-dimensional network structure with extremely high porosity, which not only acts as a barrier to prevent electrolyte leakage but also provides a channel for the transmission of ions in the electrolyte, thereby effectively guaranteeing the high photoelectric conversion efficiency of the cells. The membrane was observed to withstand the conditions of hot-press (110 °C), and exhibited good thermal stability and mechanical strength, which are critical for the long-term stability and safety of the cells. The photovoltaic characteristics and stabilities of QS-DSSCs were compared with DSSCs based on an ionic liquid electrolyte (L-DSSC). QS-DSSCs with an 80 μm thick nanofiber electrolyte membrane showed a conversion efficiency of 8.63%, whereas an identical cell based on the corresponding ionic liquid electrolyte showed an efficiency of 9.30%. The stability test showed that, under indoor and outdoor conditions, after 390 h, the L-DSSCs failed. Meanwhile, the QS-DSSCs also maintained 84% and 77% of the original efficiency. The results show that, compared to the liquid electrolyte, the design of the quasi-solid electrolytes based on electrospun PVDF nanofiber membrane not only demonstrates the high conversion efficiency of DSSCs but also enhances the stability of the DSSCs, which provides the possibility for the fabrication of solar cells with higher efficiency and stability.

Unexpectedly high piezoelectricity of electrospun polyacrylonitrile nanofiber membranes

Polyvinylidene fluoride (PVDF) and its co-polymers are among the best piezoelectric polymer materials owing to the large piezoelectric coefficient and mechanical properties. Processing PVDF polymers into fibrous membranes through electrospinning can largely increase the piezoelectricity. In contrast, polyacrylonitrile (PAN), an amorphous polymer, is known to have a much lower piezoelectricity than PVDF. Herein, we report an unusually-high piezoelectric feature of electrospun PAN nanofiber membranes. When a small piece of PAN nanofiber nonwoven membrane (e.g. 5 cm2) was subjected to compressive impact, it can generate up to 2.0 V of voltage, the electrical outputs of which are even higher than that of PVDF nanofiber membranes at the same condition. Such unexpected piezoelectric properties were found to originate from the high content of planar Sawtooth PAN conformation within nanofibers. Electric charges in PAN nanofibers also contributed to the energy conversion. The energy conversion capability can be further enhanced by increasing fiber orientation within fibrous membrane. Also, the working area and thickness of nanofibrous membranes as well as impact conditions influenced piezoelectric outputs. The energy generated is usable and can power commercial LEDs. These unexpected discovery may inspire to develop novel piezoelectric materials and devices.

All-Nanofiber-Based Ultralight Stretchable Triboelectric Nanogenerator for Self-Powered Wearable Electronics

The flexible and stretchable electronics have been considered as next-generation electronics. Stretchable triboelectric nanogenerators (S-TENGs) with both multifunction and comfort have become a hot field of research for wearable electronic devices recently. Here, we designed an all-nanofiber-based, ultralight, S-TENG that could be softly attached on skins for motion energy harvesting and self-powered biomechanical monitoring. The S-TENG consisted of only two nanofiber membranes: a polyvinylidene fluoride nanofiber membrane (PVDFNM) supported by thermoplastic polyurethane nanofiber membrane (TPUNM) was used as the frictional layer, and a multiwalled carbon nanotube (MWCNT) conductive material screen-printed on the TPUNM was used as the electrode layer. Due to the excellent stretchability of TPUNM, the S-TENG could generate electricity under various types of deformation, and regains its original performance after intense mechanical extension, even if it is partially cut or damaged. Owing to the great elect...

Development of Novel Membranes Based on Electro–spun Nanofibers and Their Application in Liquid Filtration, Membrane Distillation and Membrane Adsorption

Electro–spinning is known as a simple and versatile method to produce nonwoven membranes made out of nanofibers. A wide range of polymers and blends can be used to yield nanofibers. Commonly used membrane polymers such as cellulose acetate (CA), polysulfone (PSU) and polyvinylidene fluoride (PVDF) have been successfully electro–spun to form nonwoven nanofiber membranes for water filtration. Investigations have revealed that electro–spun nanofibrous membranes (ENMs) possess high–flux rates and low transmembrane pressure. These characteristics are due to its (1) high porosity, (2) interconnected open pore structure and (3) tailorable membrane thickness. Although electro–spun membranes have been extensively studied for decades and successfully commercialized as air filtration membrane, they have not been applied for water treatment. The nanofiber membranes were used recently at the Industrial Membrane Research Laboratory of the University of Ottawa with the collaboration of Nanoscience & Nanotechnology Initiative of the National University of Singapore for the following investigations.Removal of latex particles from water: PVDF nanofiber membranes were subjected to filtration of latex particles (0.1 to 10 μm) at the feed pressure of 0.6 bar gauge [1, 2].Seawater desalination by membrane distillation: PVDF nanofiber membranes were subjected to desalination of aqueous NaCl solutions by air gap membrane distillation [3, 4].Trihalomethanes (THMs) and haloacetic acids (HAAs) removal by carbonized polyacrylnitrile (PAN) nanofiber membranes [5, 6].

Polyvinylidene fluoride nanofiber coated polypropylene nonwoven fabric as a membrane for lithium-ion batteries

Polyvinylidene fluoride (PVdF) membranes in spite of having many critical properties necessary for lithium-ion batteries, do not have satisfying thermal and mechanical resistance. The goal of this study was to combine the good mechanical and thermal properties of PP nonwoven fabric with the excellent electrochemical properties of PVdF nanofibers to exploit a high-performance membrane for lithium-ion batteries. This work reports the preparation of PVdF nanofiber membranes using electrospinning on a polypropylene (PP) spunbonded nonwoven fabric and an aluminum foil followed by a hot-pressing treatment. The morphology and size of the membranes were studied by the scanning electron microscopy. The tensile strength of the membrane with the PP support was superior to the PVdF membrane. Thermal stability of the prepared membranes was determined using the TGA method and the dimensional stability was investigated by measuring the shrinkage ratio at 105 °C. The results have shown that the PVdF/PP membrane was thermally more stable than the PVdF and the commercial Celgard 2325 membranes. The batteries using PVdF/PP membrane exhibited higher electrochemical oxidation limit, better cycling performance and less discharge capacity fading during 100 cycles compared to PVdF and Celgard membranes. The results of this study showed that PVdF/PP membrane is a promising advanced membrane in lithium-ion batteries.