Investigation of Redox Active Oligomers for Nonaqueous Flow Batteries
Authors: Kowalski Jeffrey A , Greco Katharine , Cao Yu , Moore Jeffrey S , Brushett Fikile R. 
Published: February 2020

Redox flow batteries show promise for grid-scale energy storage due to their simple manufacturing, decoupled power and energy, and long lifetimes1,2. However, state-of-the-art flow batteries utilizing aqueous electrolytes and transition metals are too expensive to meet the U.S. Department of Energy’s long range cost targets3 spurring research activities aimed to reducing system cost. Nonaqueous RFBs seek to lower battery costs through increased energy density enabled by high voltage nonaqueous electrolytes with high concentrations of redox materials. Redox active organic compounds are of particular interest due to their tunable molecular structure and potential for low cost synthesis4.
Recent work has suggested that using redox active macrostructures, such as redox active oligomers (RAOs)5, polymers (RAPs)6, and colloids (RACs)7, could reduce RFB costs as fluorinated ion-exchange membranes can be replaced by inexpensive size-selective separator. However, the effects of using macrostructures, instead of monomers, on electrode kinetics, species transport, and electrolyte properties are not well understood. Here, we begin to deconvolute these effects by examining the electrochemical and solution properties of a series of RAOs using electrochemical, flow cell, and analytical techniques. This work provides insights on design directions for next-generation active species.
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