Redox flow batteries go organic

Wang, Wei; Sprenkle, Vince L.

doi:10.1038/nchem.2466

Cited by 120 publications

(77 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[12,13] In the last few years, RFBs based on organic redox molecules, such as quinones, phenothiazine, nitroxides, viologens, and pyridines [14][15][16][17] have experienced a great deal of interest, becoming one of the hottest topics in electrochemical energy storage (see Table S1 in the Supporting Information). [18,19] Regardless of the chemical nature of the electroactive species and the type of electrolytes, most RFBs rely on ion-selective membranes to separate the two redox electrolytes and to prevent the crossover of active compounds while allowing the migration of charge carriers. It is worth mentioning that membranes are not employed in some hybrid RFBs in which one of the active species is a solid, such as Zn, [20,21] Cd, [22] lithium, [23] or graphite.…”

mentioning

confidence: 99%

A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

et al. 2017

View full text Add to dashboard Cite

Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short‐lifetimes, and expensive ion‐selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane‐free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof‐of‐concept of a membrane‐free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L−1, and is able to deliver 90 % of its theoretical capacity while showing excellent long‐term performance (coulombic efficiency of 100 % and energy efficiency of 70 %).

show abstract

mentioning

confidence: 99%

A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

et al. 2017

View full text Add to dashboard Cite

show abstract

“…[4,5] Despite these advantages, high system prices (> $500kWh À1 in 2014) [6,7] have severely limited the commercial deployment of RFBs. [6,10] Although not commercially viable yet, NAqRFBs promise an umber of advantages over aqueous systems, including broader electrochemical windows (3-4 V), [1,11,12] which could enable higherc ell energy densities and aid in the implementation of multi-electrontransfer materials. [8,9] Recent techno-economic analyses predicted that both aqueous and nonaqueous( NAq) RFBs couldr each this aggressive target by decreasing manufacturing costs, advancing materials performance, and improving cell architecture.…”

Section: Introductionmentioning

confidence: 99%

“…To facilitate integration of a4he nergy-storage system,t he United States Department of Energy( DOE) Office of Electricity Deliverya nd Energy Reliability set at arget price of $150 kWh À1 ,i ncluding costs for installation and power-conditioning equipment. [12] Additionally,awide range of NAq solvents and supportings alts are available, and rational functionalization of the active speciescan be used to tailor physicochemical and electrochemical properties, [13] providing multiple pathways for device optimization and price reduction. [6,10] Although not commercially viable yet, NAqRFBs promise an umber of advantages over aqueous systems, including broader electrochemical windows (3-4 V), [1,11,12] which could enable higherc ell energy densities and aid in the implementation of multi-electrontransfer materials.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of a Supporting‐Salt‐Free Nonaqueous Redox Flow Battery Utilizing Ionic Active Materials

et al. 2017

View full text Add to dashboard Cite

Nonaqueous redox flow batteries (NAqRFBs) are promising devices for grid-scale energy storage, but high projected prices could limit commercial prospects. One route to reduced prices is to minimize or eliminate the expensive supporting salts typically employed in NAqRFBs. Herein, the feasibility of a flow cell operating in the absence of supporting salt by utilizing ionic active species is demonstrated. These ionic species have high conductivities in acetonitrile (12-19 mS cm ) and cycle at 20 mA cm with energy efficiencies (>75 %) comparable to those of state-of-the-art NAqRFBs employing high concentrations of supporting salt. A chemistry-agnostic techno-economic analysis highlights the possible cost savings of minimizing salt content in a NAqRFB. This work offers the first demonstration of a NAqRFB operating without supporting salt. The associated design principles can guide the development of future active species and could make NAqRFBs competitive with their aqueous counterparts.

show abstract

“…18,30,31,38,39,43,49 This study explores how variations in RFB performance due to supporting electrolyte and membrane selection impacts system cost. We focus on aqueous electrolytes, as opposed to nonaqueous electrolytes, 12,50,51 due to the higher technology-readiness level of AqRFBs and, consequently, the larger amount of associated device information for grid-relevant operation. First, we identify governing physical parameters, namely the membrane ASR, electrolyte conductivity, electrolyte viscosity, and cell potential, which significantly impact RFB cost.…”

Section: A3884mentioning

confidence: 99%

“…Physically, ν 2 represents the ratio of chargetransfer and ion-conduction rates in the porous electrode. [12] θ is the dimensionless limiting current ( Equation 13), defined as the ratio between the exchange and limiting current densities (i l , A m −2 ). Physically, θ represents the ratio of charge-transfer and mass transfer rates in the porous electrode.…”

Section: Computing Cell Area Specific Resistancementioning

confidence: 99%

The Critical Role of Supporting Electrolyte Selection on Flow Battery Cost

Milshtein

Darling

Drake

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

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...

show abstract

Redox flow batteries go organic

Cited by 120 publications

References 6 publications

A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

Feasibility of a Supporting‐Salt‐Free Nonaqueous Redox Flow Battery Utilizing Ionic Active Materials

The Critical Role of Supporting Electrolyte Selection on Flow Battery Cost

Contact Info

Product

Resources

About