Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

Wedege, Kristina; Dražević, Emil; Kónya, Dénes; Bentien, Anders

doi:10.1038/srep39101

Cited by 260 publications

(310 citation statements)

References 40 publications

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“…At this point, spontaneous reduction of ferricyanide shifts the arrow further to the left, e.g. t 2 , restricting the SOC range of both sides and causing precipitous capacity fade. It is important to distinguish two separate capacity fade regimes in this experiment.…”

Section: Materials Interactions and Ph Effects: Stability Of Fe(cn)mentioning

confidence: 99%

“…transition metals, traditionally used for the redox-active components of flow batteries, these new organic and organometallic compounds may be susceptible to molecular decomposition, leading to an additional mechanism for flow battery charge storage capacity fade. 2 Typically, capacity fade in conventional flow batteries can occur through various mechanisms such as precipitation of reactant species or crossover of these species through the membrane. 3,4 Some of these sources of capacity loss are theoretically reversible while others are not.…”

mentioning

confidence: 99%

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Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Goulet

Aziz

2018

J. Electrochem. Soc.

207

334

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We present an unbalanced compositionally-symmetric flow cell method for revealing and quantifying different mechanisms for capacity fade in redox flow batteries that are based on molecular energy storage. We utilize it, accompanied in some cases by a corresponding static-cell cycling method, to study capacity fade in cells comprising anthraquinone di-sulfonate, di-hydroxy anthraquinone, iron hexacyanide, methyl viologen, and bis-trimethylammoniopropyl viologen. In all cases the cycling capacity decay is reasonably consistent with exponential in time and is independent of the number of charge-discharge cycles imposed. By introducing pauses at various states of charge of the capacity-limiting side during cycling, we show that in some cases the temporal fade time constant is dependent on the state of charge. These observations suggest that molecular lifetime is dominated by chemical rather than electrochemical mechanisms. Growing interest in redox flow batteries (RFBs) for grid-scale energy storage has prompted development of new redox-active organic and organometallic molecules synthesized from commonly available raw materials containing earth-abundant elements such as carbon, nitrogen and oxygen. Flow batteries based upon these synthetic compounds might achieve lower electrolyte capital costs than current vanadium-based technologies without the scarcity risks associated with finite resources.1 To become a cost-effective solution for matching of intermittent renewable energy supply to demand, these flow batteries should retain most of their capacity over decadal time scales. As opposed to the elements of the periodic table, e.g. transition metals, traditionally used for the redox-active components of flow batteries, these new organic and organometallic compounds may be susceptible to molecular decomposition, leading to an additional mechanism for flow battery charge storage capacity fade.2 Typically, capacity fade in conventional flow batteries can occur through various mechanisms such as precipitation of reactant species or crossover of these species through the membrane.3,4 Some of these sources of capacity loss are theoretically reversible while others are not. Some are related to device engineering, such as electrolyte leakage, whereas others are intrinsic to the electrolyte chemistry. RFBs that rely upon electrolytes with different dissolved redox-active species on either side, such as the chromium/iron cell, suffer from irreversible crossover of these species unless their electrolytes are balanced by putting both species on both sides, thereby doubling the cost of active materials.5 a The all-vanadium RFB was developed to avoid these problems by having a single common redox-active species on both sides of the cell such that any asymmetric crossover of active species could be reversed by rebalancing the electrolytes by simple remixing. 6 Other examples of capacity fade that can be recovered by electrolyte rebalancing methods include those due to heterogeneous side reactions, such as hydrogen evolution, or fro...

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Section: Materials Interactions and Ph Effects: Stability Of Fe(cn)mentioning

confidence: 99%

mentioning

confidence: 99%

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Goulet

Aziz

2018

J. Electrochem. Soc.

207

334

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“…[15] Desirable attributes in these three categories often trade off against each other. [15] Desirable attributes in these three categories often trade off against each other.…”

mentioning

confidence: 99%

A Phosphonate‐Functionalized Quinone Redox Flow Battery at Near‐Neutral pH with Record Capacity Retention Rate

Goulet

Pollack

et al. 2019

Advanced Energy Materials

246

228

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high cost limits their usage in grid-scale systems. Among the most promising solutions are redox-flow batteries (RFBs), which store the electro-active chemical species separately from the power-generating electrode stack, through which the reactants are pumped during operation. This design allows the energy capacity of the entire system to be scaled independently of its maximum power output so that cost-effective long-duration discharge can be achieved. [2] All-vanadium systems now have the largest market-share among RFBs, but their penetration is limited by the relatively low Earth-abundance and high cost of vanadium. [3] In contrast, the low cost of some organic molecules and the Earth-abundance of carbon offer promising advantages of redox-active organics for massive penetration of grid-scale energy storage. [4] Moreover, the chemical tunability of organic molecules permits improvements in solubility, redox potential, and stability, which can enhance the energy density, power density, and lifetime of a battery.There have been numerous reports regarding RFB chemistries based on quinone, [4a,c,5] viologen, [4b,6] ferrocene, [6a,c] alloxazine, [4d] nitroxide radical motifs, [4b,7] and phenazine [7c,8] in the past four years which, while demonstrating promising performance, fall short of meeting all of the technical requirements for practical deployment. Due to the generally low chemical stability of these reactants, most existing systems experience high temporal capacity fade rates on the order of 0.1-10% per day, which limits their long-term use and renders most of these chemistries unsuitable for commercialization. Voltage trades off against stability in many cases. This is most readily apparent in cells utilizing substituted viologens against substituted ferrocenes, where adequate stability has been accompanied by large compromises in open-circuit voltage (OCV). [6a,c,d] Recently, we reported a negative electrolyte (negolyte) comprising 4,4-((9,10-anthraquinone-2,6-diyl)dioxy) dibutyrate (2,6-DBEAQ), [9] that combines high chemical stability with an OCV of ≥1.0 V against a potassium ferri/ferrocyanide positive electrolyte (posolyte). This flow battery exhibited a capacity fade rate of 0.04% per day, which was the lowest of any quinone species at the time. In the current work, we report an aqueous RFB employing a phosphonate-functionalized A highly stable phosphonate-functionalized anthraquinone is introduced as the redox-active material in a negative potential electrolyte (negolyte) for aqueous redox flow batteries operating at nearly neutral pH. The design and synthesis of 2,6-DPPEAQ, (((9,10-dioxo-9,10-dihydroanthracene-2,6-diyl) bis(oxy))bis(propane-3,1-diyl))bis(phosphonic acid), which has a high solubility at pH 9 and above, is described. Chemical stability studies demonstrate high stability at both pH 9 and 12. By pairing 2,6-DPPEAQ with a potassium ferri/ferrocyanide positive electrolyte across an inexpensive, nonfluorinated permselective polymer membrane, this near-neutral quinone flow bat...

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“…[47][48][49][50] Huskinson et al introduced a novel flow battery system for energy storage, in which they coupled a quinone redox species with a bromine positive half-cell. Their metal-free cell showed high power density during discharge and high cycling efficiency.…”

Section: Reactant Chemistry Requirements and Selectionmentioning

confidence: 99%

“…These quinone compounds can moreover be tuned for their standard reduction potentials as well as their solubility by adding different functional groups to the structure. 50,52 When quinones are reduced reversibly to their respective hydroquinones, the two carbonyl groups change to two hydroxyl groups (C−OH). Their electrochemical reactions involve two electrons in either acidic 47,48 or alkaline conditions, 45,49 as shown in Eqs.…”

Section: Reactant Chemistry Requirements and Selectionmentioning

confidence: 99%

Evaluation of Redox Chemistries for Single-Use Biodegradable Capillary Flow Batteries

Ibrahim

Alday

Sabaté

et al. 2017

J. Electrochem. Soc.

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The rate of battery waste generation is rising dramatically worldwide due to increased use and consumption of electronic devices. A new class of portable and biodegradable capillary flow batteries was recently introduced as a solution for single-use disposable applications. The concept utilizes stored organic redox species and supporting electrolytes inside a dormant capillary flow cell which is activated by the dropwise addition of aqueous liquid. Herein, various organic redox species are systematically evaluated for prospective use in disposable capillary flow cells with regards to their electrochemical characteristics, solubility, storability and biodegradability. Qualitative ex-situ techniques are first applied to assess half-cell solubility, redox potential and kinetics, followed by quantitative in-situ measurements of discharge performance of selected redox chemistries in a microfluidic cell with flow-through porous electrodes. Para-benzoquinone in oxalic acid and either hydroquinone sulfonic acid or ascorbic acid in potassium hydroxide are identified for the positive and negative half-cells, respectively, yielding a maximum discharge power density of 50 mW/cm 2 . A prototype capillary flow battery using the same redox chemistries demonstrates robust cell voltages above 1.0 V and maximum discharge power of 1.9 mW. These results show that practical primary battery performance can be achieved with biodegradable chemistries in a disposable device. The market demand for small-size single-use electronic devices such as portable sensors and diagnostic devices has been rising drastically in recent years. The power needs of such devices have so far been met by Li-ion batteries and other primary battery technologies, resulting in a consequent rise in their consumption. These batteries often contain heavy metals and strong electrolytes which make them one of the most hazardous components of electronic waste.1 In addition, the majority of the primary Li batteries used globally are not recycled nor properly disposed of, thus ending up in landfills without regulations.2 In applications that do not require long discharge times and have modest capacity requirements such as medical devices, these batteries are not even fully discharged before being disposed of. This requires further resources for re-extracting the materials if not recovered, which is not sustainable and raises concerns about the abundance of these resources. The end-of-life fate of these batteries and their life cycle assessment therefore only justifies the use in rechargeable applications beyond hundreds of cycles.3,4 These issues trigger a worrying concern about associated future environmental hazards from the battery waste generation and urgently call for novel alternatives, tightened environmental policies and switching the linear consumption habit of "take-make-dispose" for these primary batteries into a circular economy model. This approach utilizes novel concepts such as green electronics and cradle-to-cradle design to eliminate waste from the conc...

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Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

Cited by 260 publications

References 40 publications

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods

A Phosphonate‐Functionalized Quinone Redox Flow Battery at Near‐Neutral pH with Record Capacity Retention Rate

Evaluation of Redox Chemistries for Single-Use Biodegradable Capillary Flow Batteries

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