Query: Vanadium Redox battery

title: Hybrid proton exchange membrane of sulfonated poly(ether ether ketone) containing polydopamine coated carbon nanotubes loaded phosphotungstic acid for vanadium redox flow battery
abstract: A hybrid membrane of sulfonated poly(ether ether ketone)/polydopamine coated carbon nanotubes loaded phosphotungstic acid (S/DCNTs HPW) is proposed for vanadium redox flow battery (VRFB) With the DCNTs HPW nanofillers as the proton donor and acceptor, a high proton conductivity and low vanadium ions permeability of the S/DCNTs HPW hybrid membranes is demonstrated owing to the formed acid base interaction. Specifically, S/DCNTs HPW 1 gives higher ion selectivity (25.4 x 103 S min cm 3) than that of pristine SPEEK (4.3 x 103 S min cm 3) and Nafion 117 (4.0 x 103 S min cm 3) Cell utilizing S/DCNTs HPW 1 reveals excellent coulombic efficiency (98.2 99.4% and energy efficiency (89.5 69.0% under the current density of 50 160 mA cm 2, and a 34.5% charge capacity retention under 100 cycles is achieved based on the excellent membrane structure and chemical stability. The S/DCNTs HPW 1 membrane shows a self discharge time of 576 h, which is longer than that of the Nafion 117 membrane (23 h) Thus, the S/DCNTs HPW hybrid membranes are suggested for potential use as alternative PEMs in the VRFB system.

title: Novel highly efficient branched polyfluoro sulfonated polyimide membranes for application in vanadium redox flow battery
abstract: Branched polyfluoro sulfonated polyimide (BPFSPI) membranes with different degree of branching and degree of sulfonation are designed and prepared for application in vanadium redox flow battery (VRFB) The optimized BPFSPI 10 50 membrane exhibits a similar proton conductivity (2.94 x 10 2 S cm 1) as that of the commercial Nafion 212 membrane (3.20 x 10 2 S cm 1) and a much higher membrane selectivity (3.16 x 105 S min cm 3) than Nafion 212 membrane (0.42 x 105 S min cm 3) Meanwhile, BPFSPI 10 50 membrane is durable in V(V) H2SO4 solutions for more than 30 d. Both coulomb efficiency (CE) and energy efficiency (EE) of BPFSPI 10 50 membrane are higher than those of Nafion 212 membrane (CE: 94.2 98.9% vs 73.9 94.9% EE: 68.0 86.9% vs 67.7 77.9% in VRFB (40 200 mA cm 2) test. Besides, BPFSPI 10 50 membrane displays slower self discharge rate and excellent discharge capacity retention compared to Nafion 212 membrane. Furthermore, the VRFB with BPFSPI 10 50 membrane shows very stable CE and EE >98% and 76% over 200 charge discharge cycles. Accordingly, the BPFSPI 10 50 membrane with superior cost performance ratio has an outstanding prospect for application in VRFB.

title: Accelerated design of vanadium redox flow battery electrolytes through tunable solvation chemistry
abstract: Operational stability of electrolytes is a persistent impediment in building redox flow battery technology. Stabilizing multiple vanadium oxidation states in aqueous solution is a primary challenge in designing reliable large scale vanadium redox flow batteries (VRBs) Here we demonstrate that rationally selected ionic additives can stabilize the aqua vanadium solvate structures through preferential bonding and molecular interactions despite their relatively low concentrations =0.1 M) The competing cations (NH4+ and Mg2+ and bonding anions (SO42 PO43 and Cl introduced by bi additives are used to tune the vanadium solvation chemistry and design an optimal electrolyte for VRB technology. Such molecular engineering of VRB electrolytes results in enhancement of the operational temperature window by 180% and energy density by more than 30% relative to traditional electrolytes. This work demonstrates that tunable solvation chemistry is a promising pathway to engineer an optimal electrolyte for targeted electrochemical systems.

title: Vanadium redox flow battery working even at a high current density by the adoption of tris(hydroxymethyl) aminomethane functionalized acidified carbon nanotube catalyst
abstract: aminomethane (Tris) functionalized carbon nanotube (Tris CNT) is newly suggested as a catalyst promoting the redox reactivity of vanadium ions in vanadium redox flow battery (VRFB) This Tris CNT is synthesized by a condensation reaction between the carboxyl group of carboxylic acid functionalized carbon nanotube (CA CNT) and the amine group of Tris. Since one Tris molecule has three hydroxyl groups, the surface of Tris CNT consists of abundant oxygen functional groups that play a key role in facilitating the redox reaction of vanadium ions. To confirm the viability of Tris CNT as a catalyst for VRFB, its chemical and electrochemical properties are evaluated. As a result, the reactivity of Tris CNT increases by 136 and 159% for V2+/V3+ and VO2+/VO2+ reactions when compared to those of CA CNT. Besides, at a high current density of 250 mA cm 2, VRFB using Tris CNT shows a capacity of 19.1 Ah L 1 and energy efficiency of 69% while those of VRFB using CA CNT are 13.0 Ah L 1 and 63% The above results show that the use of the new Tris CNT catalyst has a strong influence on the improvement in the performance of VRFB.

title: Superior acidic sulfate ester group based high conductive membrane for vanadium redox flow battery
abstract: Proton conductive group is essential to provide ion transport site and tune micro phase separation in proton exchange membranes for vanadium redox flow battery (VRFB) while nearly all the fabrication methods are based on the benchmark sulfonic acid group. Herein, the sulfate ester group OSO3H) with superior acidity is proposed as a novel proton conductive group to achieve high proton transport at lower IECs, therefore disentangles the trade off between vanadium crossover and conductive ion diffusion. The electron withdrawing ester oxygen atom endows sulfate ester group with 27 kJ mol 1 lower proton binding energy than the sulfonic acid group, leading to higher proton dissociation ability and better micro phase separation. The 1,3 propanediol cyclosulfate grafted polybenzimidazole with IEC of 1.85 (OPBI OSO3H 1.85) reaches comparable area resistance (0.19 O cm 2) to the sulfonic acid grafted polybenzimidazole with much higher IEC of 2.95 (OPBI SO3H 2.95) but 19.1% decrease in vanadium permeability. The cell assembled with OPBI OSO3H 1.85 achieves high energy efficiency of about 86.7% and low decay of discharge capacity (0.41% per cycle) superior to that of OPBI SO3H 2.95 (0.51% per cycle) and Nafion 212 (0.71% per cycle) The sulfate ester group is proved to be chemically stable in H2SO4/vanadium environment.

title: Ion selective redox active anion exchange membrane: Improved performance of vanadium redox flow battery
abstract: In sight understanding of synergetic and trade off behaviour between chemical and structural properties of emerging redox active membrane separator for batteries is necessary for high performance and widespread adoption of technologies. Our aim is to provide sustainable solution such as stable membrane with fast ionic transport (low resistivity) and impervious nature for redox active species that leads to deleterious capacity fade and materials underutilization. We report architecture of redox active anion exchange membranes (AEMs) by free radical polymerization using tert butylmethaacrylate (tBuMA) vinylimidazole (VIm) and vinyl ferrocene (VFc) The VFc acts as redox responsive species (ferrocenium ion) due to protonation under operating conditions. These ion selective redox active membranes offer chemical modularity, high conductivity, stability, and prevents VO2+ cross over, necessary for improved vanadium redox flow battery (VRFB) performance. The fundamental electrochemistry of redox active membranes is fascinating, due to redox peaks (Fc/Fc+ in voltammetry. Suitable redox active membrane separator exhibits 98.0% current efficiency corresponding to 85.0% voltage efficiency at 60 mA cm 2 in VRFB operation. Therefore, AEMs with redox active functional moieties can open a new avenue for efficient VRFB and various electrochemical applications.

title: Novel ether free sulfonated poly(biphenyl) tethered with tertiary amine groups as highly stable amphoteric ionic exchange membranes for vanadium redox flow battery
abstract: The development of cost effective, ion selective and highly stable non fluorinated hydrocarbon membranes is crucial to the vanadium redox flow battery (VRFB) Herein, we report a facile approach to designing a novel ether free amphoteric ionic exchange membrane (AiEM) grafted with long flexible alkyl side chains with zwitterionic groups, prepared by superacid catalyzed polycondensation with post modification. Both FTIR and H1NMR spectra confirm the polymer's chemical structure. An acid base interaction that can form between sulfonic group and tertiary amine group contributes to the high stability, low swelling ratio and vanadium ion permeability of the AiEM. Owing to the unique amphoteric structure and connected ion channels, optimized TA15 SPBP membrane achieves a high proton conductivity of 0.116 S cm 1 25 together with superb ion selectivity of 14.7 x 105 S min cm 3 compared to that of Nafion212 membrane. Consequently, the VRFB assembled with the TA15 SPBP membrane exhibits superior coulombic/energy efficiencies of 99.1%/87% at 80 mA cm 2 with respect to Nafion212 (92.9%/78.2% Importantly, the highly stable ether free backbone and acid base interaction greatly improve the structural stability of the membrane. During an 1188 cycling test, the TA15 SPBP membrane keeps almost unchanged efficiencies at 80 mA cm 2 with excellent capacity retention (80.5% in comparison with Nafion212 (11.3% during the first 200 cycles, thus demonstrating the promising prospects for VRFB applications.

title: Preparation and characterization of the side chain quaternized poly(phthalazinone ether ketone)s with phenyl groups for vanadium redox flow battery
abstract: A series of new side chain substitution poly (phthalazinone ether ketone)s with benzyl chloride moieties (CMPPEK P) were synthesized through the chloromethylation of poly (aryl ether ketone)s containing pendant phenyl groups (PPEK P) The content of side chain phenyl groups in the PPEK P was controlled by the feed ratios of 4 (4 hydroxyphenyl) 2,3 phthalazin 1 ketone to 4 (3 phenyl 4 hydroxyphenyl) 2,3 phthalazin 1 ketone during polymerization process. The chemical structures of PPEK P and CMPPEK P were assessed by 1H NMR and FTIR spectroscopy. Based on the characterization results, a new anion exchanged membrane (QAPPEK P) was prepared by amination reaction used for vanadium redox flow batteries. The ion exchange capacity of QAPPEK P membranes (0.21 0.88 mmol g 1) was related to the content of side chain phenyl groups. The cell performance of QAPPEK P membrane was increased with the increasing values of IEC. Compared with Nafion 115, QAPPEK P 50 displayed higher voltage efficiency (82.8% vs. 76.9% and energy efficiency (80.2% vs. 76.5% at the current density of 140 mA/cm2. Furthermore, the efficiencies of QAPPEK P 50 remained stable for 150 cycles and there was no obvious change in its structure.

title: Reductive Precipitation of Vanadate by Shewanella putrefaciens and Its Applicability to Vanadium Redox Flow Battery
abstract: Vanadate reduction by a bacterium, Shewanella putrefaciens, was experimentally investigated under aerobic and anaerobic conditions. Lactate was supplied as an electron donor. Unlike the abiotic control sample, the color of the samples inoculated with S. putrefaciens changed from yellow to deep green under both conditions over time, which indicated that V(V) became microbially reduced. Precipitates formed in the microbial samples and results of the XRD analysis showed that this was a V(IV) bearing mineral. The concentrations of total dissolved V in microbial samples decreased over time, which suggested that S. putrefaciens reduced soluble V(V) followed by the precipitation of insoluble V(IV) solids. The results imply that microbial reduction of V(V) may be economically applied to the production of V(IV) electrolytes which demand a high cost for the operation of vanadium redox flow batteries.

title: High performance membranes based on pyridine containing poly (aryl ether ketone ketone) for vanadium redox flow battery applications
abstract: This reported study describes an effort to produce durable membranes for high performance vanadium redox flow batteries (VRFB) The reported novel, positively charged membranes are derived from pyridine containing poly(aryl ether ketone ketone) (PyPEKK) and are prepared using an environmentally friendly method. Basic pyridine groups on the polymer backbone serve as proton acceptor sites and these electron rich, polar sites establish proton transport channels, which provide PyPEKK membranes with an area resistance as low as 0.15 O cm2, which is comparable to Nafion 212 (0.13 O cm2) The novel PyPEKK membranes have low vanadium permeability due to the Donnan repulsion between the positively charged protonated pyridine groups and the vanadium ions. Consequently, the resulting dense structure of these PyPEKK membranes produce an impressive energy efficiency in VRFB (89.0% at 80 mA cm 2, and 80.1% at 180 mA cm 2) The PyPEKK membrane exhibit stable performance of 1000 cycles and low oxidation. These PyPEKK membranes are highly promising candidates for VRFB application.