Redox flow batteries (RFBs) are recognized as one of most promising battery technologies to integrate intermittent renewable energy sources (e.g., solar and wind). Particularly, organic redox flow batteries are highly attractive for sustainable and economical large-scale energy storage as redox active molecules are synthetically tunable, sustainable, and potentially inexpensive. Through rational molecular engineering, we have developed and applied redox active molecules including viologen, ferrocene, and TEMPO for both aqueous and non-aqueous organic redox flow batteries (AORFBs and NAORFBs). In this presentation, we will discuss electrochemical studies of methyl viologen/ferrocene RFBs in aqueous and non-aqueous supporting electrolytes. Through the case studies of methyl viologen/ferrocene RFBs, this presentation aims to provide a direct technological comparison of AORFBs and NAORFBs regarding solution chemistry, energy efficiency, current performance, and cycling stability.

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