Organic Electroactive Materials for Aqueous Redox Flow Batteries.

Organic electroactive materials take advantages of potentially sustainable production and structural tunability compared to present commercial inorganic materials. Unfortunately, traditional redox flow batteries based on toxic redox-active metal ions have certain deficiencies in resource utilization and environmental protection. In comparison, organic electroactive materials in aqueous redox flow batteries (ARFBs) have received extensive attentions in recent years for low-cost and sustainable energy storage systems due to their inherent safety. This review aims to provide the recent progress in organic electroactive materials for ARFBs. We first classify the main reaction types of organic electroactive materials in ARFBs to provide an overview on how to regulate their solubility, potential, stability and viscosity. Then, the organic anolyte and catholyte in ARFBs are summarized according to the types of quinones, viologens, nitroxide radicals, hydroquinones etc, and how to increase the solubility by designing various functional groups is emphasized. We next present the research advances of the characterization of organic electroactive materials for ARFBs. Future efforts are finally suggested to focus on building neutral ARFBs, designing advanced electroactive materials through molecular engineering, and resolving problems of commercial applications. This article is protected by copyright. All rights reserved.