Reversible redox chemistry in azobenzene-based organic molecules for high-capacity and long-life nonaqueous redox flow batteries

Journal Article · Fri Jul 31 00:00:00 EDT 2020 · Nature Communications

DOI:https://doi.org/10.1038/s41467-020-17662-y· OSTI ID:1657203

Zhang, Leyuan ^[1]; Qian, Yumin ^[1]; Feng, Ruozhu ^[2]; Ding, Yu ^[1]; Zu, Xihong ^[1]; Zhang, Changkun ^[1]; Guo, Xuelin ^[1]; Wang, Wei  ^[2]; Yu, Guihua ^[1]

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1. Univ. of Texas, Austin, TX (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Redox flow batteries (RFBs), often categorized as aqueous and nonaqueous systems, represent a type of large-scale energy storage technology for renewable energy resources. Redox-active organic molecules have recently drawn extensive interests in RFBs as promising active materials due to their elemental abundance, structural diversity and high tunability of properties, but employing organic molecules in nonaqueous systems is far limited in terms of useable capacity and cycling stability. Here we introduce a class of azobenzene-based organic compounds with the azo group as redox-active center in the p-conjugated structure as new active materials to realize high-performance nonaqueous RFBs with long cycling life and high capacity. By screening suitable organic solvents with high solubility and conductivity, the azobenzene organic molecule was capable to achieve a stable long cycling with a low capacity decay of 0.014% per cycle and 0.16% per day over 1000 cycles. And the stable cycling of electrolytes under a high concentration of 1 M was also realized, delivering a high reversible capacity of ~46 Ah L^-1. The unique lithium-coupled redox chemistry accompanied with a voltage increase was observed and revealed by experimental characterization and theoretical simulation. With the reversible two-electron redox activity of azo group in p-conjugated structures, azobenzene as an azo-aromatic molecule represents a class of promising redox-active organics for potential grid-scale energy storage systems.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Electricity (OE); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC05-76RL01830; 57558
• OSTI ID: 1657203
• Report Number(s): PNNL-SA-152812
• Journal Information: Nature Communications, Vol. 11; ISSN 2041-1723
• Publisher: Nature Publishing Group
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
Energy storage
materials for energy and catalysis