Mechanism-Based Design of a High-Potential Catholyte Enables a 3.2 V All-Organic Nonaqueous Redox Flow Battery

Yan, Yichao; Robinson, Sophia G.; Sigman, Matthew S.; Sanford, Melanie S.

doi:10.1021/jacs.9b07345

Cited by 122 publications

(142 citation statements)

References 51 publications

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“…Subsequently, other organic redox-active molecules were successfully demonstrated in the redox flow batteries, employing both aqueous [67][68][69] and non-aqueous electrolytes, showing the great promises. [70,71] Analogous liquid-state organic electrodes were also explored in rechargeable non-flow battery systems, which contain solid electrolyte membranes that physically separate the two electrodes. The alkali metal biphenyl complexes were successfully utilized as the liquid-state anode with their low redox potential close to that of the elemental alkali metal electrode.…”

Section: Recent Paradigm Shifts In Utilizing Redox-active Organic Commentioning

confidence: 99%

Redox‐Active Organic Compounds for Future Sustainable Energy Storage System

Lee

Hong

Kang

2020

Advanced Energy Materials

175

126

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to be promising for rechargeable battery chemistries that emit low carbon footprints during production. [4-8] Redox-active organic compounds, that is, chemicals composed of unlimited resources such as carbon, hydrogen, oxygen, nitrogen, and sulfur, among them have exhibited the great potential as a carbon-neutral option, possibly exploiting the bio-derived materials and not relying on the scarce transition metal resources, in all organic-based LIBs, owing to their chemical diversity and functional versatility. [6-8] Despite their promising potential and intensive research efforts to date, replacing the commercial electrodes in LIBs with these new electrode materials remains a great challenge due to the short cycle life and the low energy density in the electrode-and system-level. However, recent alternative approaches have demonstrated that the utilization of redox-active organic compounds in battery systems other than LIBs can be more promising, taking advantage of their chemical and functional flexibilities in diverse electrochemical configurations. In this essay, we highlight the progressive shift in exploiting the redox-active organic compounds in new battery platforms for future ESSs, as well as offer an overview of the advancements achieved during the past decade. 2. Basic Operating Mechanisms of Organic Electrode Materials The working principle of the redox-active organic compounds as active materials in electrodes can be classified into three categories, that is, n-type, [9] p-type, [10] and bipolar-type, [11] based on their capabilities to receive or release electrons in their neutral state during the electrochemical reaction. Figure 1 schematically illustrates the three types of redox reaction with the molecular structures of the representative redox-active compounds. [6,8,12] Most of the known redox-active organic compounds follow one or more of these redox mechanisms in rechargeable batteries. The n-type electrochemical reaction represents the reduction of the neutral-state organic compound electrodes, forming negatively charged molecular states, which can be reversed during the oxidation reaction. In lithium batteries, the n-type "cathodes" readily accept electrons and the corresponding number of Li-ions during the discharge process, thus generally require Li-containing anodes. Contrarily, the n-type "anodes" can be paired with the conventional LIB cathodes, such as LiMeO 2 (Menickel, cobalt, manganese, aluminum, etc.), LiFePO 4 , or LiMn 2 O 4 , which intrinsically Utilizing redox-active organic compounds for future energy storage system (ESS) has attracted great attention owing to potential cost efficiency and environmental sustainability. Beyond enriching the pool of organic electrode materials with molecular tailoring, recent scientific efforts demonstrate the innovations in various cell chemistries and configurations. Herein, recent major strategies to build better organic batteries, are highlighted: diversifying charge-carrying ions, modifying electrolytes, and utilizing liquid-type organic el...

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Section: Recent Paradigm Shifts In Utilizing Redox-active Organic Commentioning

confidence: 99%

Redox‐Active Organic Compounds for Future Sustainable Energy Storage System

Lee

Hong

Kang

2020

Advanced Energy Materials

175

126

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“…In addition to preventing cross contamination, symmetric ORFBs can access three different oxidation states of the electrolyte within the same compartment, resulting in a charged to one polarity or to the opposite polarity via one-electron cycles in opposite directions. To date, only three examples of symmetric ORFBs have been reported, (Figure 1, green box), [31][32][33] and these either possess a high OCV with low cyclability (Figure 1, example iv), or a better reliability (max 100 cycles) but a small OCV (Figure 1 (Cyclability = capacity (Q) retention >90% after n cycles) with their electrolyte couples: (i), 28 (ii), 29 (iii), 30 (iv), 31 (v) 32 and (vi) 33 .…”

Section: Toc Graphicsmentioning

confidence: 99%

“…These values are higher than other known anolytes, 29,42,43 and about four times higher than recent catholytes studied, which is an advantage for our DMQA + . [28][29][30]43,44 The electron transfer rate constants (k 0 ) were determined using the Nicholson method (Equation S2, Figures S5-6), 45 where the k 0 = 2.5(5) × 10 -3 cm s -1 for C + /C • redox couple is almost similar to that of the C •++ /C + redox pair k 0 = 2.3(1) × 10 -3 cm s -1 and both are comparable to recent electrolytes developed for RFB. 28,30 The persistent oxidized and reduced species of C + , and their fast and identical electronic kinetics, suggest that this electrolyte is suitable for ORFB application.…”

Section: Toc Graphicsmentioning

confidence: 99%

Symmetric, Robust, and High-voltage Organic Redox Flow Battery Model Based on a Helical Carbenium Ion Electrolyte

Moutet¹,

Veleta²,

Gianetti

2020

Preprint

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Redox flow batteries (RFBs) represent a promising technology for grid-scale integration of renewable energy. Redox-active molecular pairs with large potential windows have been identified as key components of these systems. However, cross-contamination problems encountered by the use of different catholyte and anolyte species still limits the development of reliable organic RFBs. Herein, we report the first use of a helical carbenium ion, with three stable oxidation states, as electrolyte for the development of symmetric cells. Cyclic voltammo-amperometric studies were conducted in acetonitrile to assess the essential kinetic properties for flow battery performance and cycling stability of this molecule. The selected [4]helicenium ion was then evaluated by using mono- and bi-electronic cycling experiments, resulting in 745 and 80 cycles respectively, with near-perfect capacity retention. This helical carbenium ion based electrolyte achieved a proof-of-principle 2.12 V open circuit potential as an all-organic symmetric RFB.<br>

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“…Whereas viologens and their progeny are promising as active species in redox flow batteries (RFBs), [9][10][11] their organoboron analogues have yet to be explored for similar applications. Viologens have been extensively explored as nonaqueous electrolytes, highlighted by results from Sanford and co-workers, [12] who have shown such compounds to be viable catholytes.…”

Section: Introductionmentioning

confidence: 99%

“…Such systems tend to have limited stability and/or solubilities on top of incomplete discharge through each redox event. [11,18] To summarize, a catholyte for nonaqueous redox flow batteries should have a highly negative reduction potential, a low molecular mass per electron transferred, and good solubility in all redox states. Sanford and co-workers have shown the viability of using diquat and viologens as catholytes in RFBs.…”

Section: Introductionmentioning

confidence: 99%