The Influence of Free Acid in Vanadium Redox‐Flow Battery Electrolyte on “Power Drop” Effect and Thermally Induced Degradation

Roznyatovskaya, Nataliya; Fühl, Matthias; Roznyatovsky, Vitaly A.; Noack, Jens; Fischer, P.; Pinkwart, Karsten; Tübke, Jens

doi:10.1002/ente.202000445

Cited by 12 publications

(5 citation statements)

References 24 publications

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“…Likewise, the membrane aged for three years at the first cell (3y_first-cell) demonstrates a significant reduction in the cycling performance at high current densities, resulting in a large standard deviation of the CE-values. Specifically, in each discharge cycle a remarkable power-drop effect can be observed that is most probably caused by the decreased conductivity due to blocking of the membrane channels [ 47 ]. Membrane 3y_middle-cell exhibits the same effect only in the first cycles.…”

Section: Resultsmentioning

confidence: 99%

Systematic Characterization of Degraded Anion Exchange Membranes Retrieved from Vanadium Redox Flow Battery Field Tests

et al. 2021

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Commercially available anion exchange membranes were retrieved from VRFB field tests and their degradation due to the various operation conditions is analyzed by in-situ and ex-situ measurements. Ion exchange capacity, permeability and swelling power are used as direct criteria for irreversible changes. Small-angle X-ray scattering (SAXS) and Differential scanning calorimetry (DSC) analyses are used as fingerprint methods and provide information about the morphology and change of the structural properties. A decrease in crystallinity can be detected due to membrane degradation, and, in addition, an indication of reduced polymer chain length is found. While the proton diffusion either increase or decline significantly, the ion exchange capacity and swelling power both are reduced. The observed extent of changes was in good agreement with in-situ measurements in a test cell, where the coulombic and voltage efficiencies are reduced compared to a pristine reference material due to the degradation process.

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Section: Resultsmentioning

confidence: 99%

Systematic Characterization of Degraded Anion Exchange Membranes Retrieved from Vanadium Redox Flow Battery Field Tests

et al. 2021

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“…8,29,30 The vanadium fresh electrolyte was prepared by a ratio of 2:5 M VOSO 4 •xH 2 O and H 2 SO 4 dissolved in deionized water with constant stirring for 2−3 h. In this electrolyte, H 2 SO 4 solution was used to increase the ionic conductivity, and it provides the hydrogen ions and helps with the reversible, V +5 to V +4 redox reactions. 6,14,26,27,53,54 The charge−discharge study voltage was maintained at 1.8−0.8 V throughout the study.…”

Section: Charge−discharge Studies For Vrfb and Irfbmentioning

confidence: 99%

Synergetic Functionalization of the ZnS@ASCs Biocomposite: For Enhanced Electrochemical Performance of Redox Flow Batteries and Supercapacitors

Basavaraj Chavati,

Kumar Basavaraju,

Nayaka Yanjerappa

et al. 2024

ACS Appl. Electron. Mater.

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Redox flow batteries and supercapacitors are attracting significant attention worldwide because of their roles in grid-level energy storage and smaller-scale applications. Both of these technologies play unique roles in the operation of electrochemical energy storage devices. An investigation of ZnS@ASCs composite materials shows their excellent electrochemical performance. The cost-effective, efficient, and straightforward synthesis of ZnS and their composites with bioactivated carbon was performed using a hydrothermal technique. In the context of redox flow batteries (RFBs), the ZnS@ASCs composite material was utilized as a positive electrode with an area of 132 cm2. It acted as an electrocatalyst for both vanadium redox flow batteries (VRFBs) and iron redox flow batteries (IRFBs). The stability of the ZnS@ASC-treated graphite felt electrode was demonstrated up to 200 cycles for VRFBs and 25 cycles for IRFBs, resulting in satisfactory Coulombic efficiencies (CEs) of 86.66% and 89.26% for VRFB and IRFB, respectively. Furthermore, the ZnS@ASCs composite material is applied as a coating onto a Toray carbon sheet and is utilized as the active electrode for supercapacitor applications. This working electrode exhibited a significantly high specific capacitance of 1070.80 F/g at 4 mA/g in a sulfuric acid (H2SO4) solution. The electrode maintained impressive CEs of 97.41% and 95.87% of its initial performance after undergoing 3500 charge–discharge cycles. Notably, the ZnS@ASCs composite material has been shown to be an efficient and exceptional electrochemically active material for various energy storage devices.

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“…To this end, assuming the same decay mechanisms hold, temperature may provide a means to perform accelerated degradation studies on materials that are proposed as being "stable" at room temperature in prior publications. [88][89][90] Polarization of a full cell.-To demonstrate the impact of temperature on a full cell, we pre-charged 0.1 M MEEPT and 0.1 M MEEV-TFSI 2 redox pairs (both in a 0.5 M TEA-TFSI solution in PC) to nearly achieve the theoretical room-temperature cell OCV of 1.11 V at 50% SoC. 47 Polarization behavior of the redox flow cell is shown in Fig.…”

Section: Flow Cell Testingmentioning

confidence: 99%

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

Quinn,

Ripley,

Matteucci

et al. 2023

J. Electrochem. Soc.

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The impact of cell temperature is a relatively underexplored area within the burgeoning field of nonaqueous redox flow batteries (NAqRFBs). Here, we investigate the effect of elevated temperature on the performance of nonaqueous redox electrolytes and associated flow cells. Using a model compound, N-(2-(2-methoxyethoxy)-ethyl)phenothiazine (MEEPT), in a propylene-carbonate-based electrolyte, we experimentally measure the temperature dependence of relevant physicochemical properties (i.e., electrolyte conductivity, viscosity, diffusivity) and electrochemical characteristics (i.e., chemical and electrochemical reversibility) across a temperature range of 30 °C to 70 °C. We then perform flow cell studies, finding that while ohmic and mass transport resistances decrease significantly with increases in temperature for the MEEPT/MEEPT+· redox couple, accessible electrolyte capacity gradually reduces at temperatures > 50 °C. Ex-situ, post-test characterization using microelectrode voltammetry suggests that this capacity fade is due to instability of the MEEPT radical cation. Finally, using MEEPT as a posolyte and a model viologen negolyte (bis(2-(2-methoxyethoxy)ethyl)viologen), we assemble a full cell and perform polarization analyses, observing a 2× increase in the peak power density when the operating temperature is increased from 30 °C to 70 °C. Broadly, this work highlights opportunities for systematic engineering of nonaqueous electrolytes and flow cells for higher power operation at elevated temperatures.

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The Influence of Free Acid in Vanadium Redox‐Flow Battery Electrolyte on “Power Drop” Effect and Thermally Induced Degradation

Cited by 12 publications

References 24 publications

Systematic Characterization of Degraded Anion Exchange Membranes Retrieved from Vanadium Redox Flow Battery Field Tests

Systematic Characterization of Degraded Anion Exchange Membranes Retrieved from Vanadium Redox Flow Battery Field Tests

Synergetic Functionalization of the ZnS@ASCs Biocomposite: For Enhanced Electrochemical Performance of Redox Flow Batteries and Supercapacitors

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

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