Phenyl Acrylate-Based Cross-Linked Anion Exchange Membranes for Non-aqueous Redox Flow Batteries
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PROVIDER: S-EPMC10510496 | biostudies-literature | 2023 Jul
REPOSITORIES: biostudies-literature
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Project description:Anion exchange blend membranes (AEBMs) were prepared for use in Vanadium Redox Flow Batteries (VRFBs). These AEBMs consisted of 3 polymer components. Firstly, PBI-OO (nonfluorinated PBI) or F6-PBI (partially fluorinated PBI) were used as a matrix polymer. The second polymer, a bromomethylated PPO, was quaternized with 1,2,4,5-tetramethylimidazole (TMIm) which provided the anion exchange sites. Thirdly, a partially fluorinated polyether or a non-fluorinated poly (ether sulfone) was used as an ionical cross-linker. While the AEBMs were prepared with different combinations of the blend polymers, the same weight ratios of the three components were used. The AEBMs showed similar membrane properties such as ion exchange capacity, dimensional stability and thermal stability. For the VRFB application, comparable or better energy efficiencies were obtained when using the AEBMs compared to the commercial membranes included in this study, that is, Nafion (cation exchange membrane) and FAP 450 (anion exchange membrane). One of the blend membranes showed no capacity decay during a charge-discharge cycles test for 550 cycles run at 40 mA/cm² indicating superior performance compared to the commercial membranes tested.
| S-EPMC6410199 | biostudies-literature
Project description:Both cation-exchange membranes and anion-exchange membranes are used as ion conducting membranes in vanadium redox flow batteries (VRFBs). Anion-exchange membranes (AEMs) are applied in vanadium redox flow batteries due to the high blocking property of vanadium ions via the Donnan exclusion effect. In this study, novel anion-exchange blend membranes (AEBMs) were prepared, characterized, and applied in VRFBs. Bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide), poly[(1-(4,4′-diphenylether)-5-oxybenzimidazole)-benzimidazole] (PBI-OO) and sulfonated polyether sulfone polymer were combined to prepare 3-component AEBMs with 1,2,4,5-tetramethylimidazole (TMIm) for quaternization. 3-component AEBMs showed significantly enhanced chemical and mechanical properties compared with those of 2-component AEBMs, resulting in an improved performance in VRFBs. The compositions of the anion-exchange polymers in 3-component AEBMs were systematically varied to optimize the AEBMs for the redox-flow battery application. While the 3-component AEBMs showed comparable efficiencies with Nafion® 212 membranes, they displayed improved vanadium ions cross-over as was confirmed by open circuit voltage tests and capacity fade tests conducted in VRFBs. In addition, one of the synthesized 3-component AEBM had a superior coulombic efficiency and capacity retention in a charging⁻discharging test over 300 cycles at a current density of 40 mA/cm². It can thus be concluded that 3-component AEBMs are promising candidates for long-term operation in VRFBs.
| S-EPMC6027430 | biostudies-literature
Project description:Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm-2) in a laboratory-scale cell.
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Project description:Redox flow batteries (RFBs) based on aqueous organic electrolytes are a promising technology for safe and cost-effective large-scale electrical energy storage. Membrane separators are a key component in RFBs, allowing fast conduction of charge-carrier ions but minimizing the cross-over of redox-active species. Here, we report the molecular engineering of amidoxime-functionalized Polymers of Intrinsic Microporosity (AO-PIMs) by tuning their polymer chain topology and pore architecture to optimize membrane ion transport functions. AO-PIM membranes are integrated with three emerging aqueous organic flow battery chemistries, and the synergetic integration of ion-selective membranes with molecular engineered organic molecules in neutral-pH electrolytes leads to significantly enhanced cycling stability.
| S-EPMC9541571 | biostudies-literature
Project description:This study presents the preparation and electrochemical testing of sulfonated styrene-grafted poly(vinylidene fluoride) (pVDF) copolymers as proton exchange membranes (PEMs) for semi-organic redox flow batteries (RFBs) based on 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/bromine. The copolymers are synthesized via a two-step procedure, involving i) atom transfer radical polymerization of styrene (Sty) for the grafting to the pVDF backbone and ii) the sulfonation of the polystyrene grafted side chains. Copolymers with different amounts of sulfonated styrene (SSty) in the side chains (i.e., degree of sulfonation (DS)) are obtained and used for the preparation of PEMs by solution casting. The PEMs are characterized to assess their thermal, mechanical, water absorption, and ion exchange properties, to evaluate the effect of DS on membrane properties, and to select the membrane with the best overall performance for application in single cell tests. Electrochemical testing reveals that the pVDF-g-(Sty26-co-SSty14) membrane exhibits low crossover of redox species, favorable ohmic resistance, and energy efficiency. Results from single cell tests, as compared with commercial benchmarks such as Nafion 115 and Aquivion E87-12s, highlight the potential of such copolymers as alternative membranes for RFBs.
| S-EPMC11884226 | biostudies-literature
Project description:Redox flow batteries (RFBs) are promising for large-scale long-duration energy storage owing to their inherent safety, decoupled power and energy, high efficiency, and longevity. Membranes constitute an important component that affects mass transport processes in RFBs, including ion transport, redox-species crossover, and the net volumetric transfer of supporting electrolytes. Hydrophilic microporous polymers, such as polymers of intrinsic microporosity (PIM), are demonstrated as next-generation ion-selective membranes in RFBs. However, the crossover of redox species and water migration through membranes are remaining challenges for battery longevity. Here, a facile strategy is reported for regulating mass transport and enhancing battery cycling stability by employing thin film composite (TFC) membranes prepared from a PIM polymer with optimized selective-layer thickness. Integration of these PIM-based TFC membranes with a variety of redox chemistries allows for the screening of suitable RFB systems that display high compatibility between membrane and redox couples, affording long-life operation with minimal capacity fade. Thickness optimization of TFC membranes further improves cycling performance and significantly restricts water transfer in selected RFB systems.
| S-EPMC10369228 | biostudies-literature
Project description:Among various components commonly used in redox flow batteries (RFBs), the separator plays a significant role, influencing resistance to current as well as capacity decay via unintended crossover. It is well-established that the ohmic overpotential is dominated by the membrane and interfacial resistance in most aqueous RFBs. The ultimate goal of engineering membranes is to improve the ionic conductivity while keeping crossover at a minimum. One of the major issues yet to be addressed is the contribution of interfacial phenomena in the influence of ionic and water transport through the membrane. In this work, we have utilized a novel experimental system capable of measuring the ionic crossover in real-time to quantify the permeability of ionic species. Specifically, we have focused on quantifying the contributions from the interfacial resistance to ionic crossover. The trade-off between the mass and ionic transport impedance caused by the interface of the membranes has been addressed. The MacMullin number has been quantified for a series of electrolyte configurations and a correlation between the ionic conductivity of the contacting electrolyte and the Nafion® membrane has been established. The performance of individual ion-exchange membranes along with a stack of various separators have been explored. We have found that utilizing a stack of membranes is significantly beneficial in reducing the electroactive species crossover in redox flow batteries compared to a single membrane of the same fold thickness. For example, we have demonstrated that the utilization of five layers of Nafion® 211 membrane reduces the crossover by 37% while only increasing the area-specific resistance (ASR) by 15% compared to a single layer Nafion® 115 membrane. Therefore, the influence of interfacial impedance in reducing the vanadium ion crossover is substantially higher compared to a corresponding increase in ASR, indicating that mass and ohmic interfacial resistances are dissimilar. We have expanded our analysis to a combination of commercially available ion-exchange membranes and provided a design chart for membrane selection based on the application of interest (short duration/high-performance vs. long-term durability). The results of this study provide a deeper insight into the optimization of all-vanadium redox flow batteries (VRFBs).
| S-EPMC7345879 | biostudies-literature
Project description:Among various components commonly used in redox flow batteries (RFBs), the separator plays a significant role, influencing resistance to current as well as capacity decay via unintended crossover. It is well-established that the ohmic overpotential is dominated by the membrane and interfacial resistance in most aqueous RFBs. The ultimate goal of engineering membranes is to improve the ionic conductivity while keeping crossover at a minimum. One of the major issues yet to be addressed is the contribution of interfacial phenomena in the influence of ionic and water transport through the membrane. In this work, we have utilized a novel experimental system capable of measuring the ionic crossover in real-time to quantify the permeability of ionic species. Specifically, we have focused on quantifying the contributions from the interfacial resistance to ionic crossover. The trade-off between the mass and ionic transport impedance caused by the interface of the membranes has been addressed. The MacMullin number has been quantified for a series of electrolyte configurations and a correlation between the ionic conductivity of the contacting electrolyte and the Nafion® membrane has been established. The performance of individual ion-exchange membranes along with a stack of various separators have been explored. We have found that utilizing a stack of membranes is significantly beneficial in reducing the electroactive species crossover in redox flow batteries compared to a single membrane of the same fold thickness. For example, we have demonstrated that the utilization of five layers of Nafion® 211 membrane reduces the crossover by 37% while only increasing the area-specific resistance (ASR) by 15% compared to a single layer Nafion® 115 membrane. Therefore, the influence of interfacial impedance in reducing the vanadium ion crossover is substantially higher compared to a corresponding increase in ASR, indicating that mass and ohmic interfacial resistances are dissimilar. We have expanded our analysis to a combination of commercially available ion-exchange membranes and provided a design chart for membrane selection based on the application of interest (short duration/high-performance vs. long-term durability). The results of this study provide a deeper insight into the optimization of all-vanadium redox flow batteries (VRFBs).
| S-EPMC7345879 | biostudies-literature
Project description:We show the synthesis of a redox-active quinone, 2-methoxy-1,4-hydroquinone (MHQ), from a bio-based feedstock and its suitability as electrolyte in aqueous redox flow batteries. We identified semiquinone intermediates at insufficiently low pH and quinoid radicals as responsible for decomposition of MHQ under electrochemical conditions. Both can be avoided and/or stabilized, respectively, using H3 PO4 electrolyte, allowing for reversible cycling in a redox flow battery for hundreds of cycles.
| S-EPMC7891622 | biostudies-literature
Project description:Aqueous redox flow batteries that employ organic molecules as redox couples hold great promise for mitigating the intermittency of renewable electricity through efficient, low-cost diurnal storage. However, low cell potentials and sluggish ion transport often limit the achievable power density. Here, we explore bipolar membrane (BPM)-enabled acid-base redox flow batteries in which the positive and negative electrodes operate in the alkaline and acidic electrolytes, respectively. This new configuration adds the potential arising from the pH difference across the membrane and enables an open circuit voltage of ∼1.6 V. In contrast, the same redox molecules operating at a single pH generate ∼0.9 V. Ion transport in the BPM is coupled to the water dissociation and acid-base neutralization reactions. Interestingly, experiments and numerical modeling show that both of these processes must be catalyzed in order for the battery to function efficiently. The acid-base concept provides a potentially powerful approach to increase the energy storage capacity of aqueous redox flow batteries, and insights into the catalysis of the water dissociation and neutralization reactions in BPMs may be applicable to related electrochemical energy conversion devices.
| S-EPMC8228583 | biostudies-literature