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Title: Tanking up energy through atypical charging
Aqueous redox flow batteries could provide viable grid-scale electrochemical energy storage for renewable energy because of their high-power performance, scalability, and safe operation ( 1 , 2 ). Redox-active organic molecules serve as the energy storage materials ( 2 , 3 ), but only very few organic molecules, such as viologen ( 4 , 5 ) and anthraquinone molecules ( 6 ), have demonstrated promising energy storage performance ( 2 ). Efforts continue to develop other families of organic molecules for flow battery applications that would have dense charge capacities and be chemically robust. On page 836 of this issue, Feng et al. ( 7 ) report a class of ingeniously designed 9-fluorenone (FL) molecules as high-performance, potentially low-cost organic anode electrolytes (anolytes) in aqueous organic redox flow batteries (see the figure, top). These FL anolytes not only display exceptional energy storage performance but also exhibit an unprecedented two-electron storage mechanism.
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