Why are there no flow batteries with symmetric ferrocyanide electrolytes?

Thank you for this, as somebody with almost no background in chemistry, I can now appreciate just a bit more the complexity that goes into battery development. Where does one learn about this?

To give the answer its the cyanide part... which I knew already when looking at the title, without having much clue about underlying chemistry.

Good luck selling batteries full of some variant of cyanide to general public, i can almost imagine it working till people hear that keyword.