Enhanced Cyclability of Organic Aqueous Redox Flow Battery by Control of Electrolyte pH Value

An organic viologens/TEMPO-SO3K aqueous flow battery with neutral NaCl solution as supporting electrolyte was proposed, and the battery cycling process was further explored. During the charging/discharing process, the side reactions, such as hydrogen evolution reaction (HER), chlorine evolution reaction (CER) and oxygen evolution reaction (OER), inevitably occurred and changed the pH value of electrolyte, further influencing the redox reaction activity of active material. To balance the pH change, addition of alkaline solution to the anolyte was proposed. A significant enhancement of the cycling stability was observed, and only 5.4% capacity decay was presented after 1200 cycles.