Why are there no flow batteries with symmetric ferrocyanide electrolytes?

Ferrocyanide/ferricyanide couples are popular in flow batteries due to high stability, kinetics, and solubility, but they cannot serve as symmetric electrolytes. When exposed to potentials far from their redox potential, ferrocyanide decomposes, releasing iron and cyanide, which precipitate as Prussian blue or hydroxides and damage the cell. These decomposition pathways make symmetric ferrocyanide systems economically unviable and hazardous.