Because of the excellent scalability and design flexibility, redox flow batteries are especially advantageous for grid-scale energy storage. Traditional inorganic-based flow batteries are generally limited by the low energy density and high chemical costs, which greatly restricted their widespread market penetration. In this regard, organic redox-active materials have been reported as possible materials alternatives to exhibit encouraging properties and performance.^1,2 The development of organic materials have suggested a promising avenue for enabling next-generation redox flow batteries, although further improvements are still urgently needed to demonstrate their commercialization potential.

In this presentation, we will introduce our recent progress in developing aqueous organic flow battery materials and systems. Among a variety of organic candidates being investigated, a few have demonstrated high effective electron solubilities >3 M, favorable redox potentials to enable high cell voltages, and highly scalable synthesis leading to cost-effectiveness. More importantly, we have achieved basic structure-property understandings of the key factors that govern the solubility and chemical stability of organic redox-active materials. These have provided guidance for rational materials design and development strategies to harvest significantly improved energy density and cyclability of flow batteries.

References

1. X. Wei, W. Pan, W. Duan, A. Hollas, Z. Yang, B. Li, Z. Nie, J. Liu,D. Reed, W. Wang, V. Sprenkle, Materials and Systems for Organic Redox Flow Batteries: Status and Challenges. ACS Energy Lett. 2017, 2, 2187.
2. A. Hollas, X. Wei, M. Vijayakumar, Z. Nie, B. Li, D. Reed, J. Liu, V. Sprenkle, W. Wang, A Nature-Inspired, Energy-Dense Phenazine-based Anolyte for Aqueous Organic Redox Flow Batteries. Nat. Energy, accepted.

Figure 1. Cycling efficiency and capacity for an aqueous organic flow battery.