Symmetric Phthalocyanine Charge Carrier for Dual Redox Flow Battery/Capacitor Applications

Utilizing a slurry-based symmetric charge carrier coupled with a conductive carbon additive is a promising method for developing simple, low-cost, and stable hybrid electrochemical flow systems for energy storage. Here, we used a manganese nitride 1,4,8,11,15,18,22,25-octaethoxyphthalocyanine (EtOPcMnN; 1) as a five-redox-state symmetric charge carrier for slurry-based dual redox flow battery/capacitor applications. Electrochemical analyses of 1 revealed a wide voltage gap, fast heterogeneous electron-transfer rates, and excellent stability toward galvanostatic cycling. Slurry-state static cell measurements utilizing 1 with a conductive carbon additive, Ketjenblack, were performed and showed high faradaic efficiency and minimal capacity fade using a glass frit porous separator.