Stable Low-Cost Organic Dye Anolyte for Aqueous Organic Redox Flow Battery

Aqueous organic redox flow battery represents a potential solution to significantly reduce the cost of flow batteries. An ideal organic redox active material for flow battery application shall possess good stability in supporting electrolyte, fast redox reaction speed, and low manufacturing cost. In this work, a commercially available dye material was modified and evaluated in aqueous organic redox flow battery as anolyte. The desalted Basic Red 5 dye (d-BR5) exhibited reasonable solubility in acidic supporting electrolyte and stable redox performance. Two aqueous organic redox flow batteries with d-BR5 as anolyte and two different catholytes (4,5-dihydroxybenzene-1,3-disulfonic acid (BQDS) and cerium methanesulfonate (Ce(CH3SO3)3)) were evaluated in this work. The later system reached satisfactory stability in long-term cycling experiments. The cell of d-BR5 and (Ce(CH3SO3)3) exhibited an operating voltage ∼ 1.4 V, with 99.9% capacity retention after 200 cycles. The results indicated that organic dye molecules could be potential low-cost active materials for aqueous organic redox flow batteries.