PVDF-HFP Membrane Research Articles

Modification of poly (vinylidene fluoride-co-hexafluoropropylene) membranes by sulfonated poly (ether ether keton) coating for membrane distillation of textile wastewater

The textile and related industries can produce a large amount of wastewater with organic dyes pollutants which can cause uncertain environmental impacts. In this study, the improved poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hollow fiber membranes were used in a continuous air gap membrane distillation (AGMD) operation for wastewater treatment of the Hamadan textile factory, Iran. The porous membranes were fabricated by a phase-inversion process and the inner surface was coated by a thin layer of sulfonated poly (ether ether keton) (SPEEK). After SPEEK coating, the water contact angle of the membrane decreased from about 93° to 57°. The SPEEK coated membrane presented mean pore size and overall porosity of 10 nm and 82.2%, respectively. For the wastewater treatment, the improved membrane presented the water flux and color rejection of 24.7 kg/m2 h and 99.8% during 72 h of the AGMD operation, respectively. Additionally, the treated wastewater reduced to the turbidity of ∼2 NTU, total dissolved solid (TDS) of 16 mg/L and chemical oxygen demand (COD) of 10 mg/L. The coated membrane presented a reasonable anti-fouling property with a flux recovery ratio (FRR) of 91.7% after 72 h of the operation. Hence, the improved PVDF-HFP membrane can be a potential alternative for the removal of organic dyes from wastewater via a membrane distillation process.

Uniformly porous PVDF-co-HFP membranes prepared by mixed solvent phase separation for direct contact membrane distillation

Membrane distillation has gained significant interest as a promising technology for treating high-salt wastewater. However, membranes with large and nonuniform pore structures are prone to wetting, which compromises their salt rejection efficiency. In this study, a highly uniform porous poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane was designed and prepared through the mixed solvent phase separation (MSPS) method, which was utilized in direct contact membrane distillation to treat salt concentration solutions as high as 5.85 wt%. The results showed 13 % polymer concentration, 26 % octane concentration, and 90 s of cooling duration exhibited an optimal structure with an average pore size of 53 ± 3 nm, a surface porosity of 24.79 %, and a liquid entry pressure (LEP) value of 3.5 bar. The optimum MSPS PVDF-HFP membrane demonstrated a vapor flux of 27 kg m−2 h−1 and high salt rejection (more than 99.94 %), superior than that of the controlled NIPS membrane with nonuniform pore sizes and lower surface porosity. This desalination performance is comparable with the commercial PTFE membrane (99.68 %, 29 kg m−2 h−1) featuring an order of magnitude higher pore sizes and greater LEP. Importantly, the MSPS PVDF-HFP membrane maintained its high performance over the duration of a long-term experiment (>140 h).

Self-assembly of metal-organic framework (UIO-66-NO2) and MXene for wearable and high-performance flexible pressure sensor

Wearable sensor technology has garnered increasing attention among researchers. In this study, the porous metal-organic framework containing nitroxide (UIO-66-NO2) is pasted onto MXene by hydrogen bonding and then incorporated into PVDF-HFP for electrospinning to fabricate piezoelectric membranes. The porous structure of the metal-organic frameworks significantly contributes to the alignment of electric domain orientation within the piezoelectric membranes post-polarization, and the nitro of UIO-66-NO2 helps to enhance the inductive power effect of the sensor, the piezoelectric constant of the composite piezoelectric membrane reaches 26.1 pC/N, 5.8 times that of the pure PVDF-HFP membrane (4.5 pC/N). The sensitivity reaches 20.99 V/N, which is 5.75 times that of the pure PVDF-HFP sensor (3.65 V/N). We conduct an exploration into the potential mechanisms behind the enhanced piezoelectric properties resulting from the incorporation of MXene and the metal-organic framework. The fabricated flexible pressure sensor exhibits commendable cyclic stability, boasting rapid response and recovery time (20/10.8 ms). The sensor demonstrates the capability to monitor human respiration and pulse, discern various parts of the human body and their respective amplitudes, differentiate between different materials, the pressure sensor has potential applications in human-computer interaction and health monitoring.

Composite nanofibrous membranes with two-dimensional ZIF-L and PVDF-HFP for CO2 separation

Membrane gas-solvent contactors show effective CO2 capture as compared to solvent absorption. However, the overall efficiency of the capture process is compromised by the relatively low CO2 transfer rate of existing commercial membranes. Herein, we propose the integration of a two-dimensional zeolitic imidazolate framework (ZIF-L) with outstanding CO2 adsorption properties into porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibre membranes for energy-efficient CO2 separation through membrane gas absorption. Well-defined composite structures of the nanofibre membranes with ZIF-L are fabricated using the electrospinning technique. The favourable adsorption of CO2 molecules in the unique cushion-shaped cavities of ZIF-L enhances CO2 flux during both absorption and stripping processes even under mild temperature conditions when utilised in the composite nanofibre membranes. Consequently, the PVDF-HFP membrane with 5 wt% ZIF-L presents 26.7 mmol m−2 s−1 of CO2 stripping flux at 100 °C.

Lithium Dendrite Growth Suppression in Anode-Free Lithium Battery Using Bifunctional Electrospun Gel Polymer Electrolyte Membrane

Anode free Li metal battery (AFLMB) are being intensively investigating in recent years as a means to achieve higher capacity when compared with standard Li metal batteries. However, the severe electrolyte decomposition during plating/stripping cycles, that causes fast Li dendrite growth and quick capacity fading, is challenging for its commercialization. Herein, poly (vinylidene fluoride-hexafluoropropylene) polymer containing Li1.6Al0.4Mg0.1Ge1.5(PO4)3 ceramic filler (90:10 w% ratio, PVDF-HFP-10) gel polymer electrolyte (GPE) is employed for the first time in AFLMB to suppress the Li dendrite growth and homogeneous Li deposition is achieved during Li metal plating/stripping. The PVDF-HFP-10 based membrane is manufactured using electrospinning technique, which is well known and effective technique to increase the amount of crystalline β-phase of PVDF-HFP, on Cu collector foil. Particularly, a pure crystalline β-phase of PVDF-HFP has been observed in the adhesion layer sticked with Cu collector as confirmed from the analysis of Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy measurements. The adhesion layer is further investigated using X-ray absorption spectroscopy (XAS), grazing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS) techniques. The GAXRD analysis reveals Cu collector undergoes slight reconstruction of its (100) facets surface to (200) facets in the presence of the adhesion layer. Moreover, depth XPS analysis confirmed that the alignment of F atoms in the adhesion layer is toward the Cu collector which can play an important role for homogeneous Li deposition. Based on these findings, a novel approach is developed to prepare GPE, without peeling off the electrospun PVDF-HFP membrane from Cu collector to take advantage of the adhesion layer. The electrospun PVDF-HFP membrane GPE unpeeled off from its Cu collector (Cu@PVDF-HFP-10) prepared using novel method provides bifunctional applications, as electrolyte and as an artificial solid-electrolyte interphase (ASEI). The strong electrostatic interaction between the fiber sheet and its collector foil forms an adhesion layer (⁓0.5μm) which acts as ASEI prevents electrolyte decomposition. The Cu@PVDF-HFP-10|Li anode free cell enables uniform and highly compacted Li platting, excellent electrochemical performance, and high coulombic efficiency (CE) even at a high current density up to 5 mA cm− 2 (CE, 97.14%) after 200 cycles using 2 mAh cm− 2 capacity loading. Conversely, nonuniform and thick Li deposition is observed in the GPE prepared by conventional method (PVDF-HFP-10), due to poor contact between the membrane and the electrode, achieved only 90.08% CE after 100 cycles at 5 mA cm− 2. Post-cycling analyses using titration-gas chromatography (TGC) and XPS techniques indicated that the new strategy is conducive to prevent dead Li metal formation as well as to create a carbonate-free, robust, and stable SEI convenient to develop sustainable AFLMB system. Cycling performance of the Cu@PVDF-HFP-10 GPE utilized in the Cu|NMC AFLMB configuration delivered much better electrochemical performance than the PVDF-HFP-10 GPE (prepared by traditional method) and organic liquid electrolytes.

Sandwiched composite electrolyte with excellent interfacial contact for high-performance solid-state sodium-ion batteries

Solid-state sodium-ion batteries have attracted significant attention due to their rich resources, high safety, and high energy density. However, the lower ionic conductivity and inferior interfacial contact between solid-state electrolytes (SSEs) and electrodes limit their practical applications. Herein, polyvinylideneuoride-co-hexauoropropylene (PVDF-HFP) membrane is selected and a novel sandwiched composite PVDF-HFP/Na2.5Zr1.95Ce0.05Si2.2P0.8O11.3F0.7/PVDF-HFP (G-NZC0.05SPF0.7-G) SSEs is well designed. The ionic conductivity of Na3Zr2Si2PO12 is enhanced by Ce4+/F− co-doping. The effects of Ce4+ and F− doping on the crystal structure, density, and ionic conductivity for Na3Zr2Si2PO12 are well investigated. The optimal NZC0.05SPF0.7 delivers a high ionic conductivity of 1.39 × 10−3 S cm−1 at 25 ℃. Moreover, the PVDF-HFP membrane can significantly enhance the interface compatibility between NZC0.05SPF0.7 and electrodes. The as-prepared G-NZC0.05SPF0.7-G exhibits a large ionic conductivity of 1.07 × 10−3 S cm−1 at 25 ℃, wide electrochemical stability window up to 4.5 V, high critical current density of 1.2 A cm−2, and stable Na plating/stripping over 600 h at 0.3 A cm−2. The solid-state Na0.67Mn0.47Ni0.33Ti0.2O2/G-NZC0.05SPF0.7-G/Na battery delivers a remarkable cycling stability and rate capability at 25 ℃, indicating that the as-prepared G-NZC0.05SPF0.7-G has a promising application for solid-state SIBs. This study demonstrates an effective strategy to develop advanced solid-state electrolytes for solid-state SIBs.

A multifunctional fire-retardant gel electrolyte to enable Li-S batteries with higher Li-ion conductivity and effectively inhibited shuttling of polysulfides

A main huddle against the practical application of lithium-sulfur battery lies in serious safety concerns due to liquid organic electrolyte, shuttling of polysulfides and formation of lithium dendrites. Herein, we have devised an asymmetric and structurally stable gel electrolyte system to enable high ionic conductivity, flame-retardancy, and effective blockage of shuttling. Such a multi-functional gel electrolyte utilizes an electro-spun network of interwoven nano-fibers of poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) as structural scaffolds, with SiO2-polyvinyl alcohol (SiO2@PVA) suspension being loaded at one surface by blade coating. Such asymmetrically coated PVDF-HFP membranes are highly wettable that is essential to thorough gelling, with its well-connected porous channels to enable outstanding ionic conductivity above the limit by conventional Celgard separator, to accommodate huge volumetric changes over redox reactions, to shield polysulfides and fend off lithium dendrites. Ultimately, application of the gel electrolyte to a model Li-S cell with cathode containing 90% S delivered high initial capacity of 1439 mA h g−1 at 0.1C and a remarkable cycling stability over 300 cycles at 1C. The current gel electrolyte is expected to provide a valuable means for developing safe low-cost and durable Li–S batteries of practical importance.

Wastewater Treatment of Real Effluents by Microfiltration Using Poly(vinylidene fluoride–hexafluoropropylene) Membranes

Over the last decades, the growing contamination of wastewater, mainly caused by industrial processes, improper sewage, natural calamities, and a variety of anthropogenic activities, has caused an increase in water-borne diseases. Notably, industrial applications require careful consideration as they pose significant threats to human health and ecosystem biodiversity due to the production of persistent and complex contaminants. The present work reports on the development, characterization, and application of a poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) porous membrane for the remediation of a wide range of contaminants from wastewater withdrawn from industrial applications. The PVDF-HFP membrane showed a micrometric porous structure with thermal, chemical, and mechanical stability and a hydrophobic nature, leading to high permeability. The prepared membranes exhibited simultaneous activity on the removal of organic matter (total suspended and dissolved solids, TSS, and TDS, respectively), the mitigation of salinity in 50%, and the effective removal of some inorganic anions and heavy metals, achieving efficiencies around 60% for nickel, cadmium, and lead. The membrane proved to be a suitable approach for wastewater treatment, as it showed potential for the simultaneous remediation of a wide range of contaminants. Thus, the as-prepared PVDF-HFP membrane and the designed membrane reactor represent an efficient, straightforward, and low-cost alternative as a pretreatment step for continuous treatment processes for simultaneous organic and inorganic contaminants' remediation in real industrial effluent sources.

Hierarchical structure design of electrospun membrane for enhanced membrane distillation treatment of shrimp aquaculture wastewater

Electrospun fibrous membranes with superhydrophobicity can reduce membrane wettability and maintain a long-term stable desalination process during membrane distillation (MD). In this study, we developed a novel approach to prepare superhydrophobic poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) electrospun membranes (EMs) by constructing hierarchical microtextures on membrane surfaces via a template printing strategy. PVDF-HFP membranes with printed surface microtextures were successfully prepared using a stainless-steel mesh (SSM) template as a fiber collector. For the injection rate of 1.0 mL/h and the solvent weight ratio of N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) of 1:1, the membrane exhibited optimal printed microtextures when electrospun at the temperature of 30 ± 2 °C and relative humidity of 70 ± 5 %. The microtexture template structure provides hierarchical micro- and nano-roughness on the membrane surface. The optimal membrane exhibits superhydrophobicity, with a static contact angle of water (WCA) of 158° and a low water sliding angle (WSA) of 8.5°. In the direct contact membrane distillation (DCMD) for treating shrimp farm wastewater, the initial permeation flux of the optimal membrane was as high as 33.45 kg·m−2·h−1. The superhydrophobic membrane exhibited a stable permeation flux of 29.06 kg·m−2·h−1 (only a 13 % reduction in flux) after long-term DCMD for 72 h, which portrays great potential for practical wastewater treatment, especially in nutrient-rich aquaculture wastewater.

Free-standing and binder-free nickel polymeric nanofiber membrane for electrocatalytic oxidation of ethanol in alkaline solution

In-situ chemical reduction technique was exploited to fabricate free-standing and binder-free active nanocatalyst materials for direct ethanol fuel cells using nickel nanoparticles onto polyvinylidenefluoride-co-hexafluoropropylene membrane [Ni/PVdF-HFP]. Homogeneously distributed nickel nanoparticles with face-centered cubic structure were observed onto smooth membrane surfaces. Cyclic voltammetric measurements indicated the enhanced activity of Ni/PVdF-HFP membrane for oxidizing the alcohol molecules in NaOH solution. The measured oxidation current density increased with increasing the added ethanol concentration into the supporting electrolyte up to 0.64 M. Some kinetic parameters were calculated such as the charge transfer coefficient (α), Tafel slope and exchange current density values to record 0.468, 369 mV dec−1 and 1.28 μA cm−2, respectively. The three dimensional nanostructure of these fabricated metallic membranes and the increased number of their active voids could provide largely exposed surface areas for adsorbed alcohol molecules. The good stability of nickel nanoparticles onto PVdF-HFP membrane surface with minimum leaching level during prolonged ethanol oxidation in alkaline solution can offer unique possibilities for utilizing these polymeric electrocatalyst structures for energy production applications.

Recovery of CaSO4 and NaCl from sub-soil brine using CNT@MOF5 incorporated poly(vinylidene fluoride-hexafluoropropylene) membranes via vacuum-assisted distillation

The recovery of salts from sub-soil brine can fulfil the demand for the salts and chemicals for the industries and mitigate the problem of fresh water at the same time. This study reported the performance of a vacuum-assisted membrane distillation crystallization (VMDCr) for CaSO4 and NaCl salts recovery from sub-soil brine. The facile one-step synthesis of porous MOF5 and CNT@MOF5 composites was also reported. Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) mixed matrix flat-sheet membranes incorporated with 1 wt% of MOF5 and CNT@MOF5 were used for VMDCr. The membranes and materials were characterized by scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) analyses. The incorporation of CNTs to MOF5 did not affect the MOF5 crystallinity, confirmed by XRD and FT-IR. The MOF5 and CNT@MOF5 incorporated PVDF-HFP matrix membranes (designated as M-ZM and M-CZM, respectively) showed rough and porous morphology. Moreover, the M-CZM showed improved porosity and number of pores than the M-ZM membrane. As a result, M-CZM produced 2.1 times the flux than the pristine PVDF-HFP membrane facilitating faster crystallization. In the density span of 15.83°Be' to 24.5°Be', CaSO4 precipitated over the membrane surface, and complete precipitation of CaSO4 was achieved once the feed (sub-soil brine) reached 24.5°Be'. NaCl crystals started forming on the membrane surface after the density of the feed reached 25°Be'. The NaCl salt precipitated completely once the sub-soil brine density reached 28.5°Be'. The SEM and XRD analyses of the recovered monoclinic CaSO4 and cubic NaCl crystals revealed their good geometrical and high purity. This study concludes that the M-CZM membrane can improve the membrane properties for faster salt crystallization from sub-soil brine.

Superamphiphobic blood-repellent surface modification of porous fluoropolymer membranes for blood oxygenation applications

Biomedical gas exchange membranes used for blood oxygenation, including extracorporeal membrane oxygenators (ECMO) and artificial lung technology, have suffered from the insufficient hemocompatibility of membrane materials. Despite over 50 years of membrane oxygenation (MO) technology development, a few hydrophobic membrane materials are now available on the market. Since the hydrophobic nature of the membrane promotes protein fouling which causes thrombus formation, various anti -thrombogenic and anti-fouling coating techniques have been applied to improve the hemocompatibility and lifetime of membranes for long-term MO and implanted artificial lung applications. Here, for the first time, we have developed a superamphiphobic blood-repellent structure on a porous fluoropolymer (PVDF-HFP) based membrane for blood MO application. The PVDF-HFP nanoparticles were electrosprayed on the porous membrane surface and thermally fused to secure physical stability followed by perfluoro-silane coating with a biocompatible adhesive. A soot-like re-entrance structure was successfully generated on the membrane surface, resulting in high water, blood, and hexadecane contact angles over 150°. The modified membranes have excellent anti-fouling properties with competitive blood oxygen performance, implying promising surface properties for long-term MO and artificial lung applications. • The porous PVDF-HFP membrane surface was modified to have amphiphobicity. • A soot-like re-entrance nanostructure coated with perfluorocarbon silane showed liquid repellent properties. • The modified amphiphobic membrane showed resistance to fouling and wetting in contact with blood. • Competitive gas exchange performance were confirmed by a blood oxygenation test.

The influence of coating super-hydrophobic carbon nanomaterials on the performance of membrane distillation

Membrane distillation (MD), as a hybrid desalination technology with super-hydrophobic characteristics, has been emerging in the recent year. In this contest, the outstanding features of carbon-based nanomaterials have promising potential to contribute to the MD process evolution. This work presented an endeavor to impart the super-hydrophobic features of powder activated carbon (PAC) into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for DCMD applications. The FTIR indicates that the CNM was successfully coated onto the PVDF-HFP membrane which leading to higher contact angle values (from 83° to 124°, porosity (45% 86.9%) and water distillate flux at each increment in the PAC loading weigh. The novel coated membranes with 30 mg CNM led to an enhancement of the permeate flux (higher fluxes were obtained at higher CNMs loading) presented fluxes around 77 L/m2.h and exhibited a high salt rejection (> 99.9%) in most cases.

Superhydrophobic nanoparticle-coated PVDF–HFP membranes with enhanced flux, anti-fouling and anti-wetting performance for direct contact membrane distillation-based desalination

Synthesis and superposition of silicon oxide nanoparticles on the surface of PVDF–HFP membrane via one-step method provide high superhydrophobic, oleophobic and antifouling properties enhancing their performance in membrane distillation.

Side-chain grafted functional groups poly(vinylidene fluoride-hexafluoropropylene) anti-fouling fluorinated polymer membrane with tuneable hydrophobicity for distillation

We prepared side-chain grafted functional groups poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) fluorinated membranes to fine control hydrophobic and anti-fouling nature of membrane for desalination of high saline water by vacuum membrane distillation (VMD) process. Different functional groups viz. tri-methoxy silane, 4-methyl styrene, and 2, 3, 4, 5, 6-penta fluoro styrene were explored for side-chain grafting with PVDF-HFP matrix to improve the hydrophobic nature. Successful grafting of functional groups was confirmed by spectral analysis, while surface morphology of different membranes was assessed by scanning electron and atomic force microscopy. Membrane performance was assessed by permeate flux, fouling resistant nature, water contact angle and long-term performance. Among different prepared membranes, 2, 3, 4, 5, 6-penta fluoro styrene grafted PVDF-HFP membrane (M-PFS) was assessed suitable for VMD with permeate water flux (36% increase compared to the pristine membrane), salt rejection (99.99%), rechargeable (anti-fouling) nature by simple water washing, and longevity. The reported M-PFS membrane with novel architecture is a promising contender for desalination of high saline water by the VMD process.

Silver nanoparticles decorated polyhedral oligomeric silsesquioxane nanocages as an effective nanoadditive for improved structural and biological properties of poly(vinylidene fluoride-co-hexafluoropropylene) nanofiltration membrane

Incorporation of a well-defined functionalized polyhedral oligomeric silsesquioxane (POSS) into a polymer matrix represents a new chemical advancement for applied membrane technology. Herein, POSS nanocages densely decorated with silver (Ag) nanoparticles (NPs) were used as effective hydrophilic and antibacterial additive. In this work, first, a facile and simple chemical reduction strategy is employed to prepare the organic–inorganic hybrid nanocages of Ag@POSS by in situ reduction of the Ag NPs with octa-ammonium molecules of POSS. These Ag@POSS nanocages were added as nanofiller for the fabrication of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanohybrid membrane. Ag@POSS nanocages added PVDF-HFP membrane exhibited formation of homogeneous and stable films compared to the unmodified polymeric membranes due to van der Waals and hydrogen bonding interactions of Ag@POSS with –CH2 groups and F atoms of polymer matrix. Pure water flux measurement of nanohybrid membrane showed that Ag@POSS PVDF membrane displays dramatic increase in the permeability (1,554.6 L/m2/h) and hydrophilicity (67°) properties. Furthermore, antibacterial activity and protein adsorption capacity of Ag@POSS PVDF membrane were evaluated by quantitative analysis of living bacterial cells and protein mass adsorption using Escherichia coli and bovine serum albumin (BSA) protein, respectively. The E. coli colonies (108 CFU/mL) on the Ag@POSS PVDF membrane samples tended to decline with 0.5 × 106 CFU/mL compared to neat PVDF-HFP membrane sample (1.3 × 108 CFU/mL). The improvement in biological properties of Ag@POSS PVDF membrane is due to the formation of Ag-octamine on the surface of POSS which lead to the formation of a boundary protection film. The surface–modified POSS with Ag NPs can be used as a nanofiller in polymeric membrane for developing high-performance permeable nanofiltration and antibacterial/antifouling polymeric membranes.

Safe gel polymer electrolytes for high voltage Li-batteries

Gel polymer electrolytes (GPEs), based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), 1 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC/DMC), so called LP30, and 1‑butyl‑1-methylpyrrolidinium hexafluorophosphate ([Py14]PF6), have been developed to improve inherent safety of the electrolyte for high voltage lithium batteries. Dry PVdF-HFP membranes, prepared with EC/DMC, were soaked in LP30 in addition to its mixtures with 30 wt% and 50 wt% [Py14]PF6 to obtain GPEs. Non-flammable character and mechanical stability enhanced via physical crosslinks of the GPEs are demonstrated with flammability tests and rheological measurements, respectively. Lithium ion conduction property in the GPEs is evaluated by means of both electrochemical impedance spectroscopy and NMR spectroscopy (Pulsed Field Gradient-PFG and relaxation time). Galvanostatic charge and discharge cycles of lithium metal batteries having LiNi0.5Mn1.5O4 as a high voltage cathode demonstrate improved electrochemical performance with coulombic efficiency above 99% and high specific capacity above 110 mAh g − 1 at C/5 throughout 150 cycles, when the GPE containing LP30 with 30 wt% [Py14]PF6 is used. The capacity retention is sufficiently high compared to the GPE without [Py14]PF6, confirming that the IL is a highly promising additive for improving battery life.

Structure and Dynamics in Self-Healing Polymer Electrolytes Based on PVDF-HFP for Battery Applications

Lithium dendrite formation is a key limitation in rechargeable Li metal batteries. Here we report on a novel polymer electrolyte with self-healing capabilities, consisting of PVdF-HFP membranes imbibed with an ionic liquid electrolyte EMIM-TFSI + LiTFSI and mechanically reinforced by alumina nanowires. Similar membranes were reported to have self-healing capability via resistance to dendrite formation at the electrode-electrolyte interface.1 We have investigated the structure and dynamics in these membranes by nuclear magnetic resonance (NMR). Double resonance and 2D NMR methods show that the EMIM cation interacts with CF3 group present in HFP, forming an ion-dipole association which may be related to the desired self-healing properties. Moreover, addition of alumina nanowires has been reported2 to increase the ionic conductivity in the membrane in addition to imparting mechanical strength. We have used pulsed field gradient (PFG) NMR to investigate how alumina nanowire doping into the PVDF-HFP-IL matrix improves the Li+ diffusivity. Additional characterizations such as electron dispersion X-ray (EDX) spectroscopy to study nanowire distribution in the polymer and ionic conductivity measurements, will also be discussed. Keywords: Ionic Liquids, Self-healing, Dendrite formation, PVDF-HFP membranes, NMR spectroscopy, EDX References Chen, T. et al. Ionic liquid-immobilized polymer gel electrolyte with self-healing capability, high ionic conductivity and heat resistance for dendrite-free lithium metal batteries. Nano Energy 54, 17–25 (2018).Kwon, S. J. et al. Influence of Al2O3 Nanowires on Ion Transport in Nanocomposite Solid Polymer Electrolytes. Macromolecules 51, 10194–10201 (2018).

Improved carbon dioxide stripping by membrane contactors using hydrophobic electrospun poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) membranes

Electrospun poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) nanofibre membranes are developed for CO2 stripping within a membrane contactor. The porous and hydrophobic nature of the membranes is ideal for membrane CO2 stripping applications, providing fast gas transport, high CO2 recovery and mechanical strength. Three different morphologies of the PVDF-HFP membranes are assessed: nanofibre membranes (NFM), bead-on-string membranes (NFM-BS) and microparticles on nanofibre membranes (NFM-MP). We illustrate that both the bead-on-string and microparticles on nanofibre membranes are more hydrophobic compared to nanofibre constructs and a traditional asymmetric control membrane. The NFM-BS and NFM-MP membranes both exhibit significantly improved CO2 stripping flux over short times, while the NFM-BS membranes provides significantly improved stripping flux over longer times (240 h) compared to all other treatments, including conventional asymmetric phase inversion membranes. The structures may also show promise for membrane distillation applications.

Synthesis of polydopamine coated tungsten oxide@ poly(vinylidene fluoride-co-hexafluoropropylene) electrospun nanofibers as multifunctional membranes for water applications

In this work, electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber membranes were loaded with tungsten oxide (WO3) nanoparticles, surface coated with polydopamine (PDA) hierarchical structures, and tested in oil/water separation, photothermal water evaporation, and degradation of ampicillin. The electrospun nanofiber membranes (ENMs) consisted of three layers and the WO3 nanoparticles were incorporated into the top layer to increase their surface exposure. These layers were then heat-pressed for dimensional stability and surface coated with PDA hierarchical structures. Characterization was conducted using microscopic, goniometric, gravimetric, and spectroscopic methods. All ENMs displayed randomly oriented, smooth microporous structure and EDS mapping revealed a uniform distribution of WO3 nanoparticles on the nanofiber matrix. WO3-blended ENMs showed improved mechanical strength, higher UV/Vis absorption, and similar thickness as pristine ENM. PDA deposition has reduced the water contact angle of pristine PVDF-HFP membrane from 130.3 to 0°, whereas, the underwater oil contact angle has increased from 55.8 to 159.7°. The PDA-coated ENMs exhibited enhanced oil/water separation with 384.3 L m−2h−1 (LMH) of flux and 97.6% oil rejection when filtered under gravity. Photothermal interfacial evaporation and ampicillin degradation tests also demonstrated the multifunctionality and exciting features of the fabricated membranes for a wide range of applications.