A Highly Soluble Organic Catholyte for Non‐Aqueous Redox Flow Batteries

Kaur, Aman Preet; Holubowitch, Nicolas E.; Ergun, Selin; Elliott, Corrine F.; Odom, Susan A.

doi:10.1002/ente.201500020

Cited by 115 publications

(106 citation statements)

References 30 publications

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“…This voltage remains above 0.60 V after increasing the current. At this SOC, a power density of 0.6 mW cm À2 can be achieved, being similar to those reported in literature for organic RFBs operating with non-aqueous electrolytes [12,13,41] (see Table S1). Figure 3 a shows the charge-discharge profile of our battery and the individual voltage profiles of each phase when charged to 35 % of SOC at low current density.…”

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confidence: 87%

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

et al. 2017

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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 %).

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confidence: 87%

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

et al. 2017

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“…For example, a brief calculation for the anthraquinone disulphonate/bromine system yields a price of $27 per kW h for the redox-active organic charge-storage materials used, which is significantly lower than the price of $81 per kW h for vanadium systems. 16 In recent years, several semi-organic, [17][18][19][20][21][22][23][24][25][26][27][28][29] metal-free organic/ inorganic 16,30 and all-organic RFBs 7,[11][12][13][31][32][33][34][35] have been reported. Commonly, two different redox-active materials are used as chargestorage materials, one within the catholyte and the other within the anolyte.…”

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confidence: 99%

A bipolar nitronyl nitroxide small molecule for an all-organic symmetric redox-flow battery

et al. 2017

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An all-organic symmetric redox-flow battery (RFB) that employs nitronyl nitroxide (NN) units as a bipolar redox-active chargestorage material was designed and investigated. An organic molecule possessing two bipolar redox-active NN units connected via a tetraethylene glycol chain was synthesized for this purpose. Owing to the ethylene glycol chain, this molecule demonstrates good solubility in organic solvents. The electrochemical behavior of the obtained compound was investigated via cyclic voltammetry (CV) measurements and it features quasi-reversible redox reactions of the NN + /NN redox couple at E ½ = 0.37 V and the NN/NN − redox couple at E ½ = − 1.25 V versus AgNO 3 /Ag, which led to a promising cell voltage of 1.62 V in a subsequent battery application. A static solution-based battery exhibits a stable charge/discharge performance over 75 consecutive cycles with a high energy efficiency of 82% and an overall energy density of the electrolyte system of 0.67 W h l − 1 . In addition, a pumped RFB test demonstrates an overall energy density of the electrolyte system of 4.1 W h l − 1 and an energy efficiency of 79%.

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“…[20][21][22][23][24][25][26] Even fewer studies have incorporated advanced flow cell designs to minimize area specific resistance (ASR) and increase area specific power density.…”

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confidence: 99%

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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A Highly Soluble Organic Catholyte for Non‐Aqueous Redox Flow Batteries

Cited by 115 publications

References 30 publications

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

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

A bipolar nitronyl nitroxide small molecule for an all-organic symmetric redox-flow battery

Towards Low Resistance Nonaqueous Redox Flow Batteries

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