On-line controlled state of charge rebalancing in vanadium redox flow battery

Rudolph, Stephen A.; Schröder, Uwe; Bayanov, I. M.

doi:10.1016/j.jelechem.2013.05.011

Cited by 69 publications

(36 citation statements)

References 11 publications

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“…Electrolyte imbalance originates from a net vanadium transport across the membrane resulting in vanadium accumulation on one side and vanadium deficiency on the other side of the electrolyte . The vanadium‐deficient side limits the capacity, which can be regenerated either with periodic remixing of the negative and positive electrolyte once the capacity reaches a critical level or continuous reflow . Increasing the membrane's barrier properties towards vanadium ions only slows down this effect .…”

Section: Introductionsupporting

confidence: 88%

“…[4] The vanadium-deficient side limits the capacity, which can be regenerated either with periodic remixing of the negative and positive electrolyte once the capacity reaches a critical level or continuous reflow. [5][6][7] Increasing the membrane's barrierp roperties towards vanadium ions only slows down this effect. [8][9][10][11] The cost of remixing for a6MWh battery that loses 1.8 %o fi ts discharge capacity per cycle at 60 %d is-charge capacity is estimated to be > 8$MWh À1 ,w hich translates to 350 000 $o ver the expected lifetimeo f2 0years (see the SupportingI nformation for details).…”

Section: Introductionmentioning

confidence: 99%

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Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes

et al. 2019

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Vanadium flow batteries are among the most promising technologies for stationary energy storage applications if their cost of storage can be further decreased. Capacity fading resulting from imbalanced vanadium crossover is a key operating cost component. Herein, a new approach is reported to avoid this cost by balancing electrolyte transport with amphoteric bilayer Nafion/meta‐polybenzimidazole membranes. Within this system, the anion‐ and cation‐exchange capacity can be tuned in a straightforward manner by changing the thickness of the respective polymer layer to balance electrolyte transport for a given current density. At high current densities, a net migrative flux of vanadium directed towards the positive side is observed owing to the higher average charge of vanadium ions present at the negative side. The coulombic repulsion between the vanadium ions and the positive charges in the membrane counteracts this migrative transport and can reverse the direction of the net vanadium flux. For a technically relevant current density of 120 mA cm−2, a PBI thickness of 3–4 μm is required to balance the vanadium crossover and to minimize capacity fading.

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Section: Introductionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes

et al. 2019

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“…18 Rudolph et al speculated that a loss of oxygen-containing functional groups on the negative electrode resulted in decreased electrode activity. 14,20 Changes in mass transport, if present, are likely attributable to changes in the electrode morphology that impact electrolyte flow. One such change may be related to fiber agglomeration observed in reference 18, which would affect the electrode tortuosity.…”

Section: Resultsmentioning

confidence: 99%

The Cell-in-Series Method: A Technique for Accelerated Electrode Degradation in Redox Flow Batteries

Pezeshki

Sacci

Veith

et al. 2015

J. Electrochem. Soc.

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We demonstrate a novel method to accelerate electrode degradation in redox flow batteries and apply this method to the all-vanadium chemistry. Electrode performance degradation occurred seven times faster than in a typical cycling experiment, enabling rapid evaluation of materials. This method also enables the steady-state study of electrodes. In this manner, it is possible to delineate whether specific operating conditions induce performance degradation; we found that both aggressively charging and discharging result in performance loss. Post-mortem x-ray photoelectron spectroscopy of the degraded electrodes was used to resolve the effects of state of charge (SoC) and current on the electrode surface chemistry. For the electrode material tested in this work, we found evidence that a loss of oxygen content on the negative electrode cannot explain decreased cell performance. Furthermore, the effects of decreased electrode and membrane performance on capacity fade in a typical cycling battery were decoupled from crossover; electrode and membrane performance decay were responsible for a 22% fade in capacity, while crossover caused a 12% fade. This paper is part of the JES Focus Issue on Redox Flow Batteries-Reversible Fuel Cells.The vanadium redox flow battery (VRFB) is a potential gridscale energy storage technology that has attracted significant research interest.1-5 The cell architecture, electrodes, and membranes have been considerably optimized, resulting in increased efficiency and power density of VRFBs.3,5-10 Other research has focused on improving energy density by enhancing vanadium solubility through the use of additives in the electrolyte solution; these compounds may also enhance electrode activity. [11][12][13] As these improvements continue, the long-term durability of VRFBs becomes an issue with strong implications for commercial viability. Therefore, methods to study component durability are of growing interest.Unlike traditional secondary batteries, VRFBs do not suffer from appreciable unrecoverable capacity fade. They promise to have long lifetimes due to the ability to rebalance the electrolyte, 14-16 which negates capacity fade and may allow them to last for thousands of cycles and for several years. While the vanadium electrolyte is stable, 17 the durability of some components in the VRFB has not been studied in detail. Changes in the electrode can result in increased activation/ charge transfer resistance and decreased mass transport; changes in the membrane may result in increased ohmic resistance in the cell. These phenomena contribute to a decrease in the capacity that can be accessed at high currents as well as to reduced energy efficiency. Herein, we present a methodology and initial findings for studying performance degradation in VRFBs. The energy efficiency loss in a typical VRFB cycling experiment is deconvoluted into contributions from decreased electrode performance and increased ohmic resistance within the membrane. The capacity fade mechanism, often attributed to crossover alone...

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“…In VRFB performance, CE is affected by the vanadium ion crossover during the unit cell operation. 52 As shown in Figure 8A, the Nafion-ASFP membrane revealed a more efficient CE performance than the commercial Nafion212 membrane. The CE of Nafion212 and Nafion-ASFP is 94.4% and 96.4% in 50th cycle, respectively.…”

Section: Resultsmentioning

confidence: 86%

“…Figure A‐C represents the cycling test results (up to 50 cycles) of CE, VE, and EE, respectively. In VRFB performance, CE is affected by the vanadium ion crossover during the unit cell operation . As shown in Figure A, the Nafion‐ASFP membrane revealed a more efficient CE performance than the commercial Nafion212 membrane.…”

Section: Resultsmentioning

confidence: 99%

Development of perfluorosulfonic acid polymer‐based hybrid composite membrane with alkoxysilane functionalized polymer for vanadium redox flow battery

et al. 2019

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Summary A new kind of alkoxy silane functionalized polymer (ASFP) is synthesized by selectively functionalized carboxyl groups as a novel inorganic precursor polymer to prepare organic‐inorganic hybrid membrane for vanadium redox flow battery (VRFB) system. The novel hybrid membrane has been fabricated by interconnection between hydrophilic domains of Nafion and ASFP functional group. The effective concentration of ASFP for hybrid membrane is 25% (wt/wt). The proton conductivity and selectivity of the hybrid membrane are comparable with those of the Nafion212 membrane, which is mainly attributed by the presence of additional hydrophilic domains in the hybrid membrane. The proton conductivity and ion exchange capacity of the Nafion‐ASFP (75:25) membrane is 0.061 S/cm and 0.68 meq/g, respectively. Remarkably, the Nafion‐ASFP membrane shows a low vanadium permeability (1.259 × 10−7 cm2/min) and high selectivity, which is an excellent advantage. As a result, the hybrid membrane shows comparable efficiency performance with Nafion212 over 50 cycles. Notably, the VRFB unit cell with Nafion‐ASFP membrane achieves higher coulombic efficiency than Nafion212. The hybrid membrane reveals a new route to develop an alternative fluorinated polymer membrane with numerous advantages especially cost‐effectiveness, homogeneous dispersion of inorganic silica precursor materials in the hybrid membrane without deterioration of mechanical strength, and lower vanadium ion crossover for VRFB system.

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On-line controlled state of charge rebalancing in vanadium redox flow battery

Cited by 69 publications

References 11 publications

Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes

Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes

The Cell-in-Series Method: A Technique for Accelerated Electrode Degradation in Redox Flow Batteries

Development of perfluorosulfonic acid polymer‐based hybrid composite membrane with alkoxysilane functionalized polymer for vanadium redox flow battery

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