Tuning Intermolecular Interactions to Enhance the Cyclability of Non-Aqueous, Organic Redox Flow Batteries.

Enhancing the electrochemical stability and reversibility of redox-active organic molecules is crucial to improve the performance of non-aqueous redox flow batteries (RFBs). Compared with the widely adopted strategy of molecular engineering, we show in this study that tuning the intermolecular interaction between the active material with the supporting electrolyte is another feasible way to address the performance of non-aqueous organic RFBs. Combined with theoretical and experimental investigations, the influence of Lewis acidity of the supporting electrolyte cations and anions on the electrochemical stability and reversibility of bipyridine-based anode material is revealed. As a demonstration, a redox flow cell based on 4,4'-bipyridine anolyte and ferrocene catholyte shows greatly enhanced performance by using supporting electrolyte composed of soft Lewis acid and soft Lewis base. This study provides an alternative, yet highly effective way to addressing the cyclability of an organic compound for non-aqueous RFBs.