Long-Cycling Aqueous Organic Redox Flow Battery (AORFB) toward Sustainable and Safe Energy Storage

Hu, Bo; Debruler, Camden; Rhodes, Zayn; Liu, Tianbiao

doi:10.1021/jacs.6b10984

Cited by 559 publications

(558 citation statements)

References 33 publications

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“…7,30 Specifically, the R = 1.0 cm 2 and R DC = 1.7 cm 2 ( Figure 10b) are 26-34% lower than suggested targets 7,30 and approach the performance of alkaline or neutral AqRFBs. [79][80][81][82] A recent modeling study of ohmiclimited NAqRFBs, in the limit of fast mass transport at 100% SOC, suggested that the lowest possible ASR would be R DC ≈3.4 cm 2 (≈89 mA cm −2 at 0.3 V overpotential); 38 our experimental work, incorporating realistic mass transfer at 50% SOC, exceeds this predicted performance by >40% for overpotentials <0.3 V.…”

Section: 76mentioning

confidence: 58%

Towards Low Resistance Nonaqueous Redox Flow Batteries

Milshtein

Barton

Carney

et al. 2017

J. Electrochem. Soc.

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Nonaqueous redox flow batteries (NAqRFBs) are a promising, but nascent, concept for cost-effective grid-scale energy storage. While most studies report new active molecules and proof-of-concept prototypes, few discuss cell design. The direct translation of aqueous RFB design principles to nonaqueous systems is hampered by a lack of materials-specific knowledge, especially concerning the increased viscosities and decreased conductivities associated with nonaqueous electrolytes. To guide NAqRFB reactor design, recent techno-economic analyses have established an area specific resistance (ASR) target of <5 cm 2 . Here, we employ a state-of-the-art vanadium flow cell architecture, modified for compatibility with nonaqueous electrolytes, and a model ferrocene-based redox couple to investigate the feasibility of achieving this target ASR. We identify and minimize sources of resistive loss for various active species concentrations, electrolyte compositions, flow rates, separators, and electrode thicknesses via polarization and impedance spectroscopy, culminating in the demonstration of a cell ASR of ca. 1.7 cm 2 . Further, we validate performance scalability using dynamically similar cells with a ten-fold difference in active areas. This work demonstrates that, with appropriate cell engineering, low resistance nonaqueous reactors can be realized, providing promise for the cost-competitiveness of future NAqRFBs. Grid-scale energy storage has emerged as a critical technology for alleviating the intermittency of renewables, 1 improving the efficiency of the existing grid infrastructure, and offering frequency or voltage regulation.2 Redox flow batteries (RFBs) are particularly attractive storage devices for energy-intensive grid applications.2,3 In a typical RFB, charge-storing active species are dissolved in liquid electrolytes, which are housed in large and inexpensive tanks. The electrolytes are pumped through a power-generating electrochemical reactor, where the active species undergo reduction or oxidation on the surfaces of porous electrodes to charge or discharge the battery. [3][4][5][6] This unique architecture offers several advantages over conventional battery systems, including decoupled power and energy scaling, long operational lifetimes, easy maintenance, simplified manufacturing, and high active-to-inactive materials ratio (particularly at long storage durations). Despite many attractive features, state-of-the-art RFBs are currently too expensive for widespread adoption.7 While the majority of RFB electrolytes are aqueous, 6 transitioning to nonaqueous chemistries could enable higher cell potentials via wider electrolyte stability windows, subsequently increasing the electrolyte energy density and reducing chemical costs. 6,[8][9][10][11] Furthermore, the use of nonaqueous solvents enables a broader palette of potentially inexpensive active materials, which could significantly lower RFB costs. 7,12 In contrast to their aqueous counterparts, nonaqueous redox flow batteries (NAqRFBs) are a nascent technology,...

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Section: 76mentioning

confidence: 58%

Towards Low Resistance Nonaqueous Redox Flow Batteries

Milshtein

Barton

Carney

et al. 2017

J. Electrochem. Soc.

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“…[40][41][42] Considering chemical stability, charged methyl viologen 31,43,44 is known to react with molecular hydrogen, making it unsuitable for use in acidic electrolytes where hydrogen evolution is a likely side reaction. 45 Finally, as for safety, metal polysulfides 27 or ferrocyanide 27,37 can undergo chemical decompositions in acid to produce toxic hydrogen sulfide or cyanide gases, respectively.…”

Section: A3884mentioning

confidence: 99%

“…18 For Na + -and Cl − -IEMs, we estimate membrane conductivity from the high-frequency intercept of full-cell impedance measurements from published flow cells employing these membranes. 27,31 As thick membranes (≥ 120 μm) were employed in the relevant studies, the high-frequency intercept on the experimental Nyquist plot is dominated by the membrane resistance. The conductivity of a NaCl-based RFB electrolyte is taken as an average value from a recent literature study.…”

Section: Estimating Materials Parametersmentioning

confidence: 99%

“…Abundant inorganic active species (e.g., metal polysulfides, 27-29 iodide 28,29 ) can be inherently inexpensive. Further, redox-active organic molecules (ROMs) are comprised of earth-abundant elements (i.e., hydrogen, carbon, oxygen, nitrogen, sulfur) and their cost is not determined by production rates of raw materials or material reserves.11 New organometallic active species, [30][31][32][33][34][35][36] as well as ROMs, show promise through the addition of functionalizing ligands, enabling rational molecular design. Typically when a new active material is discovered, the supporting electrolyte must simultaneously be tuned to facilitate its implementation.…”

mentioning

confidence: 99%

“…11 New organometallic active species, [30][31][32][33][34][35][36] as well as ROMs, show promise through the addition of functionalizing ligands, enabling rational molecular design. Typically when a new active material is discovered, the supporting electrolyte must simultaneously be tuned to facilitate its implementation.…”

mentioning

confidence: 99%

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The Critical Role of Supporting Electrolyte Selection on Flow Battery Cost

Milshtein

Darling

Drake

et al. 2017

J. Electrochem. Soc.

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Redox flow batteries (RFBs) are promising devices for grid energy storage, but additional cost reductions are needed to meet the U.S. Department of Energy recommended capital cost of $150 kWh −1 for an installed system. The development of new active species designed to lower cost or improve performance is a promising approach, but these new materials often require compatible electrolytes that optimize stability, solubility, and reaction kinetics. This work quantifies changes in RFB cost performance for different aqueous supporting electrolytes paired with different types of membranes. A techno-economic model is also used to estimate RFB-system costs for the different membrane and supporting salt options considered herein. Beyond the conventional RFB design incorporating small active species and an ion-exchange membrane (IEM), this work also considers size-selective separators as a cost-effective alternative to IEMs. The size selective separator (SSS) concept utilizes nanoporous separators with no functionalization for ion selectivity, and the active species are large enough that they cannot pass through the separator pores. Our analysis finds that SSS or H + -IEM are most promising to achieve cost targets for aqueous RFBs, and supporting electrolyte selection yields cost differences in the $100's kWh Energy storage has emerged as a key technology for improving the sustainability of electricity generation 1 by improving the efficiency of existing fossil-fuel infrastructure through load-leveling or price arbitrage, 2 alleviating the intermittency of renewables (i.e., solar, wind) to promote their broad implementation, 3 and providing high-value services such as frequency regulation, voltage support, or back-up power.2 Redox flow batteries (RFBs) are promising devices for low-cost grid energy storage due to decoupled capacity and power scaling, long operational lifetime, easy thermal management, and good safety features.2,4-9 Unlike enclosed batteries (i.e., lithium-ion, nickel-metal hydride), RFBs implement soluble redox active species dissolved in liquid electrolytes, which are stored in large, inexpensive tanks. Specifically, the electrolyte is comprised of a supporting electrolyte, which contains solvent (e.g., water) and a supporting salt (e.g., sulfuric acid, sodium chloride), and the redox active species (e.g., bromine). The electrolyte is pumped through an electrochemical stack where the active species are oxidized or reduced to charge or discharge the battery. The size of the electrochemical stack determines the power rating, while the tank volume determines the energy capacity, enabling scalability unique to the RFB architecture. The introduction of new redox chemistries is a strategy for substantially lowering the electrolyte (energy) cost contribution to the total battery cost via decreased chemical costs or increased electrolyte energy density. 23,26 Key active species characteristics in determining the RFB electrolyte cost are the solubility (M), molar mass (kg mol −1 ), number of electrons stored pe...

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Redox‐Active Inorganic Materials for Redox Flow Batteries

Luo

Debruler

et al. 2019

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Continuous growth in utilization of renewable but intermittent energy such as solar and wind will accelerate the demand for grid‐scale energy storage systems. Redox flow batteries (RFBs) have been intensively studied for large‐scale energy storage (MW/MWh), which is particularly attractive when integrated with renewable energy sources. In past decades, extensive efforts have been made to improve electrochemical performance of the RFBs by exploring various active materials, from inorganic redox‐active materials to organic redox‐active molecules. Compared to burgeoning organic RFBs, inorganic RFBs have received extensive research and development in the last several decades. A great deal of efforts has been exerted to commercialize several inorganic RFB systems such as all‐vanadium RFBs and zinc–bromine RFBs. In this article, inorganic redox‐active materials (e.g., metal salts, halides, polysulfides, polyoxometalate (POM), etc.) applied in RFBs are reviewed with a primary focus on their most recent technological advances in aqueous inorganic RFBs. The advantages and limitations of different inorganic RFBs are discussed. Further technological challenges and perspective on inorganic RFBs are also highlighted.

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Long-Cycling Aqueous Organic Redox Flow Battery (AORFB) toward Sustainable and Safe Energy Storage

Cited by 559 publications

References 33 publications

Towards Low Resistance Nonaqueous Redox Flow Batteries

Towards Low Resistance Nonaqueous Redox Flow Batteries

The Critical Role of Supporting Electrolyte Selection on Flow Battery Cost

Redox‐Active Inorganic Materials for Redox Flow Batteries

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