Half-Cell State of Charge Monitoring for Determination of Crossover in VRFB—Considerations and Results Concerning Crossover Direction and Amount

Haisch, Theresa; Ji, Hyunjoon; Holtz, Lucas; Struckmann, Thorsten; Weidlich, Claudia

doi:10.3390/membranes11040232

Cited by 16 publications

(9 citation statements)

References 45 publications

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“…On the other hand, the larger capacity loss in the case of Nafion 211 is due to the lower thickness. It should also be mentioned that the net crossover is from the negative to the positive side using Nafion membranes, mainly due to the high permeation rate of V(II) and V(III) compared to V(IV) and V(V) [12,23,[40][41][42].…”

Section: Resultsmentioning

confidence: 99%

Vanadium Redox Flow Battery Using Aemion™ Anion Exchange Membranes

2022

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The vanadium redox flow battery (VRFB) is a promising and commercially available technology that poses advantageous features for stationary energy storage. A key component of the VRFB in terms of cost and system efficiency is the membrane. In recent years, anion exchange membranes (AEMs) have gained interest in VRFB research as they in general exhibit lower vanadium crossover due to a more substantial Donnan exclusion effect. In this study, a low-resistance flow cell was developed and the electrochemical performance of Aemion™ anion exchange membranes AF1-HNN5-50-X, AF1-HNN8-50-X and AF1-ENN8-50-X were compared against commonly used cation exchange membranes, Nafion® 211 and 212. The VRFB using AF1-ENN8-50-X exhibited superior performance versus Nafion® 212 regarding cycling efficiency and rate performance. However, relatively high and comparable capacity losses were observed using both membranes. NMR analysis showed no sign of chemical degradation for AF1-ENN8-50-X by immersion in VO2+ solution for 800 h. Although Aemion™ AEMs showed good chemical and electrochemical performance, considerable electrolyte crossover was observed due to high water uptake.

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Section: Resultsmentioning

confidence: 99%

Vanadium Redox Flow Battery Using Aemion™ Anion Exchange Membranes

2022

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“…Due to the high absorbance of the electrolyte, this method was found to be unsuitable within the constraints of the current system design. Successful optical monitoring of the positive electrolyte would require a stronger light source or secondary pump system to allow for thinner optical paths, while a stronger light source and photodiode amplification may be used for the negative electrolyte [6,[17][18][19].…”

Section: Discussionmentioning

confidence: 99%

“…In the case of a balanced VRFB system (the anolyte and catholyte contain equal amounts of electrochemically available vanadium ions), the SOC may be expressed as [5][6][7][8][9]:…”

Section: Introductionmentioning

confidence: 99%

“…However, this is impractical in large-scale applications due to drift in the measured potential and the need for frequent re-calibration to avoid SOC estimation errors [4,7,12]. Although improvements to SOC estimation models have been made to reduce the need for ex situ calibration, this method suffers from poor sensitivity due to the solution potential only changing slightly over wide SOC ranges [6][7][8][9]. Density measurements may also be used for SOCs, but similarly, they are subject to poor sensitivity [7,9].…”

Section: Introductionmentioning

confidence: 99%

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State of Charge and Capacity Tracking in Vanadium Redox Flow Battery Systems

Schofield

Musilek

2022

Clean Technol.

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The vanadium redox flow battery electrolyte is prone to several capacity loss mechanisms, which must be mitigated to preserve electrolyte health and battery performance. This study investigates a simple and effective technique for the recovery of capacity loss arising from symmetrical mechanisms via automatic electrolyte rebalancing. However, chemical or electrochemical techniques must be used to mitigate capacity loss from asymmetrical mechanisms (e.g., air oxidation of V2+), which requires knowledge of the oxidation states present in the electrolytes. As such, this study assesses the suitability of SOC tracking via electrolyte absorption for independent monitoring of the anolyte and catholyte within an existing VRFB system. Testing is performed over cycling of a 40 cell, 2.5 kW with 40 L of electrolyte. Optical monitoring is performed using a custom-made flow cell with optical paths (interior cavity thicknesses) ranging from 1/4″ to 1/16″. Light transmitted through the cell by a 550 lumen white light source is monitored by a simple photodiode. The electrolyte rebalancing mechanism displayed success in recovering symmetrical capacity losses, while optical monitoring was unsuccessful due to the high absorbance of the electrolyte. Potential improvements to the monitoring system are presented to mitigate this issue.

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“…The RFB cycling test aimed to find the trade-off between the opposite trends of the ASR and vanadium permeability of the membranes, which allowed for the highest energy efficiency of the RFB cell. Composite membranes with 10, 15, and 20% w/w of VIMPPO content in the coating layer were selected for this experiment; FAP 450 and Nafion ® N115 served as performance benchmarks [55][56][57][58][59].…”

Section: Vrfb Single Cell Performancementioning

confidence: 99%

Composite Anion-Exchange Membrane Fabricated by UV Cross-Linking Vinyl Imidazolium Poly(Phenylene Oxide) with Polyacrylamides and Their Testing for Use in Redox Flow Batteries

et al. 2021

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Composite anion-exchange membranes (AEMs) consisting of a porous substrate and a vinyl imidazolium poly(phenylene oxide) (VIMPPO)/acrylamide copolymer layer were fabricated in a straightforward process, for use in redox flow batteries. The porous substrate was coated with a mixture of VIMPPO and acrylamide monomers, then subsequently exposed to UV irradiation, in order to obtain a radically cured ion-exchange coating. Combining VIMPPO with low-value reagents allowed to significantly reduce the amount of synthesized ionomer used to fabricate the mem- brane down to 15%. Varying the VIMPPO content also allowed tuning the ionic transport properties of the resulting AEM. A series of membranes with different VIMPPO/acrylamides ratios were prepared to assess the optimal composition by studying the changes of membranes properties—water uptake, area resistivity, permeability, and chemical stability. Characterization of the membranes was followed by cycling experiments in a vanadium RFB (VRFB) cell. Among three composite membranes, the one with VIMPPO 15% w/w—reached the highest energy efficiency (75.1%) matching the performance of commercial ion-exchange membranes (IEMs) used in VRFBs (Nafion® N 115: 75.0% and Fumasep® FAP 450: 73.0%). These results showed that the proposed composite AEM, fabricated in an industrially oriented process, could be considered to be a lower-cost alternative to the benchmarked IEMs.

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Half-Cell State of Charge Monitoring for Determination of Crossover in VRFB—Considerations and Results Concerning Crossover Direction and Amount

Cited by 16 publications

References 45 publications

Vanadium Redox Flow Battery Using Aemion™ Anion Exchange Membranes

Vanadium Redox Flow Battery Using Aemion™ Anion Exchange Membranes

State of Charge and Capacity Tracking in Vanadium Redox Flow Battery Systems

Composite Anion-Exchange Membrane Fabricated by UV Cross-Linking Vinyl Imidazolium Poly(Phenylene Oxide) with Polyacrylamides and Their Testing for Use in Redox Flow Batteries

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