Organic Redox Targeting Flow Battery Utilizing a Hydrophilic Polymer and Its In‐Operando Characterization via State‐of‐Charge Monitoring of The Redox Mediator

• Published in: ChemSusChem Vol. 16; no. 14; pp. e202300296 - n/a
• Main Authors: Schröter, Erik, Stolze, Christian, Meyer, Jakob, Hager, Martin D., Schubert, Ulrich S.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 21.07.2023
• Subjects: Alginates; Ammonium chloride; aqueous batteries; capacity enhancement; Figure of merit; Hydrophilicity; Methacrylamide; Monitoring; Optimization; polymer batteries; Polymers; Rechargeable batteries; redox flow battery; redox targeting; capacity enhancement; polymer batteries; aqueous batteries; redox flow battery; redox targeting
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300296

The hydrophilic poly(2,2,6,6‐tetramethylpiperdinyloxy‐4‐yl‐methacrylamide) (PTMAm) was utilized as redox target material in an aqueous organic redox targeting flow battery (RTFB). This polymer is processed into granules, which contain a conductive agent and an alginate binder. By this, a hydrophilic, yet water‐insoluble redox target can be obtained. The target was combined with the redox mediator molecule N,N,N‐trimethyl‐2‐oxo‐2‐[(2,2,6,6‐tetramethylpiperidin‐4‐yloxyl)amino]ethan‐1‐ammonium chloride (TEMPOAmide), that has been reported earlier as flow battery active material. This target/mediator combination has been characterized electrochemically and flow battery testing has been done. Furthermore, in‐operando characterization of the redox target via electrolyte state‐of‐charge (SOC) monitoring has been performed for the first time. The approach provides estimates for the redox target's SOC changes during cycling. In addition, a figure of merit – the “redox targetivity” – is proposed, which provides insights into the efficiency of the targeting reaction and supports the future optimization of materials, cell designs, and operational parameters for RTFBs. Redox targeting flow battery: A new combination of organic redox mediator and redox target is presented. Therefore, a hydrophilic polymer was processed into porous composite granules using sodium alginate, which enables aqueous slurry processing and aqueous battery utilization. Furthermore, a new figure of merit –the redox targetivity– was introduced after in‐operando state of charge measurements.