(Keynote) Opportunities and Challenges of Organic Redox Flow Batteries

Aqueous organic redox flow batteries (AORFBs) represent a promising energy storage technology for the integration of renewable energy and balancing electricity grids because of their technical merits of decoupled energy and power, sustainable and tunable redox active materials, and non-flammable and low cost aqueous supporting electrolytes. This presentation will review recent efforts in developing new flow battery chemistries, including viologen (anolyte), quinone (anolyte), TEMPO (catholyte), ferrocene (catholyte), and ferrocyanide (catholyte). The merits and drawbacks of representative acidic, pH neutral, and alkaline AORFBs will be discussed and compared. A number of research strategies will be discussed to develop high-performance redox active electrolytes to enable energy dense, durable, low-cost flow battery technologies. Particularly, this presentation emphasizes that in-depth mechanistic understandings of redox active electrolytes play crucial roles in developing advanced organic redox flow batteries towards sustainable, long-duration energy storage. References : (1) Luo, J.; Hu, B.; Hu, M.; Liu, T. L. "Status and Prospects of Organic Redox Flow Batteries towards Renewable Energy Storage", ACS Energy Lett. 2019, 4, 2220-2240. (2) Wu, W.; Luo, J.; Wang, F.; Yuan, B.; Liu, T. L. "A Self-Trapping, Bipolar Viologen Bromide Electrolyte for Aqueous Redox Flow Batteries", ACS Energy Lett. 2021, 6, 2891-2897. (3) Luo, J.; Hu, B.; DeBruler C. Zhao, Y.; Yuan B;. Hu, M.; Wu, W.; Liu, T. L. "Unprecedented Capacity and Stability of Ammonium Ferrocyanide Catholyte in pH Neutral Aqueous Redox Flow Batteries", Joule 2019, 4, 149-163. (4) Hu, B.; Luo, J.; Hu, M.; Yuan B.; Liu, T. L.* "A Neutral, Metal Free Aqueous Organic Redox Flow Battery Employing an Ammonium Anthraquinone Anolyte", Angew. Chem. 2019, 58, 16629-16636. (5) DeBruler C.; Hu, B.; Moss, J.; Liu, X. Luo, J.; Sun, Y; Liu, T. L. "Designer Two Electron Storage Viologen Anolyte Materials for Aqueous Organic Redox Flow Batteries", Chem 2017, 3, 961-978. (6) Hu, B.; DeBruler C., Rhodes, Z.; Liu, T. L. "Long Cycling Aqueous Organic Redox Flow Battery for Sustainable and Safe Energy Storage", J. Amer. Chem. Soc. 2017, 139, 1207-1214. (7) Liu, T.; Hu, B.; DeBruler, C.; and Luo, J. "Materials for Use in Aqueous Organic Redox Flow Batteries", US patent No., 10,934,258, 2021. (8) Liu, T.; Wei, X.; Sprenkle, V.; Wang, W. "Aqueous electrolytes for redox flow battery systems", US patent No. 14,690,224, 2016.