Low-Cost Redox Flow Batteries Based on Aqueous Soluble Organic Redox Materials

X. Wei, B. Li, Z. Nie, W. Duan, M. Vijayakumar, T. Liu, D. Reed, W. Wang, V. Sprenkle
Pacific Northwest National Laboratory,
United States

Keywords: energy storage, Redox Flow Batteries

Summary:

As a promising grid energy storage technology, redox flow batteries have great potential to overcome the intermittency of renewable energies and improve the grid reliability. Independent design of tank volume and stack size leads to the advantage of separating energy and power. This feature offers tremendous flexibility for different energy/power ratio applications. Traditional inorganic redox materials have suffered limited solubility, low electrochemical reactivity and/or high cost.4 Instead, organic compounds are being pursued because of their molecular diversity, structural tailorability, environmental benignity, and potentially low cost. Aqueous soluble organic (ASO) redox materials have been investigated and evaluated in several aqueous organic flow battery systems. Here we report a new aqueous organic flow battery chemistry based on low-cost ASO materials in neutral electrolytes.7 In this system, a commonly used herbicide, paraquat (i.e., methyl viologen, MV), was used as the anolyte redox material. An industrially important catalyst, 4-hydroxy-TEMPO (TEMPOL), was used as the catholyte redox material. Both compounds have remarkable high solubilities in water, >2M. Preliminary electrochemical tests (cyclic and linear sweep voltammetries) yielded a cell voltage of ~1.2 V and fast electrochemical kinetics for both compounds. Flow cell tests demonstrated excellent cycling stability over extended charge/discharge cycling . The perspectives of using ASO materials for flow batteries will be discussed.