Friedel-Crafts crosslinked highly sulfonated poly ether ether sulfone (SPEEK) membranes for Vanadium/Air Redox Flow Battery (original) (raw)
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Membranes, 2013
Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl 2 via the Friedel-Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150°C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated Membranes 2014, 4 2 for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200°C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO 2+ crossover compared to Nafion.
Low cost sulfonated poly (ether ether ketone) membranes have been successfully prepared and optimized at various sulfonation conditions by casting method for vanadium redox battery applications. The optimized SPEEK membrane was initially tested in the G1 vanadium redox battery (VRB) before being evaluated in the G2 vanadium bromide redox flow battery (V/Br), and the performance was compared to that of Nafion 117. From the G1 VRB performance tests, the energy efficiency of the membrane was found to be 77%, slightly higher than Nafion 117 which gave 73% at current density 40 mA cm À 2 . For the first time, the SPEEK membrane was evaluated in the G2 V/Br at two different ratios of bromine complexing agents and the performance was assessed from the measured cell efficiencies. At 4 mA cm À 2 , the optimum energy efficiency was 76% using SPEEK in the presence of 0.19 M MEM and 0.56 M MEP, when compared to 75% obtained with Nafion 117. Similar to Nafion 117, SPEEK also exhibits excellent chemical stability in the highly oxidizing electrolytes. The SPEEK membrane thus appears to be a promising candidate for both G1 and G2 VRB applications.
Journal of Power Sources, 2010
A series of novel organic-inorganic hybrid membranes with special microstructure, based on sulfonated poly (fluorenyl ether ketone) ionomer (SFPEK, IEC = 1.92 mequiv. g −1 ) and SiO 2 or sulfonic acid group containing SiO 2 (SiO 2 -SO 3 H), has been successfully designed and prepared for vanadium redox flow battery (VRB) application. The SiO 2 -SO 3 H is synthesized by co-condensation of tetraethoxysilane and ␥-propyl mercaptotrimethoxysilane via sol-gel process to control the same IEC with neat SPFEK. The hybrid membranes are prepared by simply adding the inorganic particles into the SPFEK solution in N,Ndimethylacetamide, followed by ultrasonic dispersion, casting and profiled temperature drying process. The morphology is examined by SEM-EDX which is applied to the top surface, bottom surface and crosssection of the hybrid membranes. The water uptake, oxidative stability, thermal property, mechanical property, proton conductivity, VO 2+ permeability and single cell performance are investigated in detail in order to understand the relationship between morphology and property of the membranes. All the hybrid membranes show dramatically improved proton selectivity at 20 • C and 40 • C when compared with Nafion117. The VRB assembled with the SPFEK/3%SiO 2 and SPFEK/9%SiO 2 membranes exhibit higher coulombic efficiency and average discharge voltage than the VRB assembled with the SPFEK membrane at all the tested current densities.
Preparation of sulfonated composite membrane for vanadium redox flow battery applications
Journal of Membrane Science, 1995
In the present studies, Daramic, which consists of ultrahighmolecular polyethylene, amorphous silica and mineral oil, was crosslinked with divinylbenzene (DVB) as a crosslinking agent and further sulfonated to obtain a cation exchange membrane for the vanadium redox cell. It was shown that the average pore size of Daramic was reduced from 0.1 to 0.02 /~m after crosslinking . The preparation and characterisation of the modified ion exchange membrane from the composite membrane with subsequent sulfonation are described. The membrane modification process results in a dramatic reduction in solvent transfer across the membrane when used in the vanadium redox cell. The ion exchange capacity (IEC) of the sulfonated composite membrane was also evaluated. The sulfonation reaction was found to be able to incorporate cation exchange groups into the composite membrane. Water transport measurements across the sulfonated composite membrane showed promising results compared with those across the composite membrane. A detailed FESEM and ~3C NMR analysis of the composite membrane and the sulfonated composite membrane have been carried out.
Proton Conducting Organic-Inorganic Composite Membranes for All-Vanadium Redox Flow Battery
Membranes
The quest for a cost-effective, chemically-inert, robust and proton conducting membrane for flow batteries is at its paramount. Perfluorinated membranes suffer severe electrolyte diffusion, whereas conductivity and dimensional stability in engineered thermoplastics depend on the degree of functionalization. Herein, we report surface-modified thermally crosslinked polyvinyl alcohol-silica (PVA-SiO2) membranes for the vanadium redox flow battery (VRFB). Hygroscopic, proton-storing metal oxides such as SiO2, ZrO2 and SnO2 were coated on the membranes via the acid-catalyzed sol-gel strategy. The membranes of PVA-SiO2-Si, PVA-SiO2-Zr and PVA-SiO2-Sn demonstrated excellent oxidative stability in 2 M H2SO4 containing 1.5 M VO2+ ions. The metal oxide layer had good influence on conductivity and zeta potential values. The observed trend for conductivity and zeta potential values was PVA-SiO2-Sn > PVA-SiO2-Si > PVA-SiO2-Zr. In VRFB, the membranes showcased higher Coulombic efficiency th...
J. Mater. Chem. A, 2013
Synthesis of chloromethylated polysulfone (CMPSF) and PSF-TMA + Cl-. CMPSF was synthesized via the Friedel-Crafts reaction following the procedure described by Avram and coworkers. 1 Details describing the chloromethylation procedure and fabrication of PSF-TMA + Clused in our lab is given in our previously published work. 2 Note: higher molecular weight PSF (~75,000), Acros Organics, was used rather than the lower molecular weight PSF (~35,000) documented in our previous work. 2 The PSF-TMA + Clfilm was then ion-exchanged to sulfate form by immersing in 1 M Na 2 SO 4 solution at room temperature during 24 hours. The 1 M Na 2 SO 4 solution was changed several times over a 24 hour period to improve the ion exchange process. The PSF-TMA + in the sulfate form was immersed and rinsed with DI water for several hours (at least 3 hours) to remove excess ions. Ionic conductivity. Electrochemical impedance spectroscopy (EIS) was used to determine the in-plane conductivity of the membrane. A membrane (in sulfate form) was placed in the conductivity cell (Teflon ® cell) in contact with 4 platinum wires. The external wires were connected to the working and counter electrodes of the potentiostat and the inner electrodes were used as working sense and reference.
Journal of The Electrochemical Society, 2014
Sulfonated Diels-Alder poly(phenylene) (SDAPP) membranes were synthesized and characterized as potential electrolyte separators for vanadium redox flow batteries. The SDAPP membranes studied had ion exchange capacities of 1.4, 1.8 and 2.3 meq/g. Transmission electron microscopy imaging shows that the ionic domains in SDAPP are roughly 0.5 nm in dimension, while Nafion has a hydrophilic phase width of around 5 nm. The sulfuric acid uptake by SDAPP was higher than that for Nafion, but the materials had similar water uptake from solutions of various sulfuric acid concentrations. In equilibration with sulfuric acid concentrations ranging from 0-17.4 mol • kg −1 , SDAPP with a IEC of 2.3 meq/g had the highest conductivity, ranging from 0.21 to 0.05 S • cm −1 , while SDAPP with a IEC of 1.8 had conductivity close to Nafion 117, ranging from 0.11 to 0.02 S • cm −1. With varying sulfuric acid concentration and temperature, vanadium permeability in SDAPP is positively correlated to the membrane's IEC. The vanadium permeability of SDAPP 2.3 is similar to that of Nafion, but permeability values for SDAPP 1.8 and SDAPP 1.4 are substantially lower. The vanadium permeation decreases with increasing electrolyte sulfuric acid concentration. Vanadium diffusion activation energy is about 20 kJ • mol −1 in both SDAPP and Nafion.
Surface Modification of Sulfonated Poly(phenylene oxide) Membrane for Vanadium Redox Flow Batteries
Journal of Nanoscience and Nanotechnology, 2020
Sulfonated poly(phenylene) oxide (sPPO) polymer is coated in a dopamine hydrochloride solution to prepare a highly durable, low-price polymer membrane for vanadium redox flow batteries (VRFBs). The polydopamine (PDA) coating on the sPPO membrane is confirmed using SEM and EDX analysis. sPPO coated with PDA exhibits decreased proton conductivity due to high resistance. However, VO+2 reducibility tests shows that the chemical stability is improved due to the introduction of the PDA coating layer on the sPPO membrane, which has a chemical structure with poor durability in VO+2 solution under the operating conditions of a VRFB. These results show that this polymer electrolyte membrane based on PDA-coated sPPO is a candidate for application in the long-term operation of VRFBs.
Membranes, 2021
A sulfonated polyimide (SPI)/Nafion blend membrane composed of a designed and synthesized SPI polymer and the commercial Nafion polymer is prepared by a facile solution casting method for vanadium redox flow battery (VRFB). Similar molecular structures of both SPI and Nafion provide good compatibility and complementarity of the blend membrane. ATR-FTIR, 1H-NMR, AFM, and SEM are used to gain insights on the chemical structure and morphology of the blend membrane. Fortunately, the chemical stability of the SPI/Nafion blend membrane is effectively improved compared with reported SPI-based membranes for VRFB applications. In cycling charge-discharge tests, the VRFB with the as-prepared SPI/Nafion blend membrane shows excellent battery efficiencies and operational stability. Above results indicate that the SPI/Nafion blend membrane is a promising candidate for VRFB application. This work opens up a new possibility for fabricating high-performance SPI-based blend membrane by introduction ...