Good luck selling batteries full of some variant of cyanide to general public, i can almost imagine it working till people hear that keyword.
> When using ferrocyanide, also consider that while this salt is relatively safe in its unaltered state, subjecting it to electrochemical abuse WILL generate free cyanide and it’s likely to pose a significant danger to you and others. For this reason, I would recommend to stay away from testing ferrocyanides in symmetric systems entirely, unless you are a trained professional and professionally well equipped to handle both the potential operational hazards and wastes generated from its decomposition products.
I don't think many people are concerned about their batteries being safe for ingestion.
The problem is free cyanide is extraordinarily dangerous in the air and you'd likely kill a lot of people before someone realized what was going on with the battery, not just that people eat batteries. Even lithium batteries honestly get pretty close to not being worth the risk for consumers, cyanide is still a bit of a step after that yet.
You can have safe battery chemistry or useful battery chemistry. (Not an expert, open to correction.)
(these things are "all relative, if the value, measured in "convenience to the customer", is high enough, ways will be found to permit sale)
Or perhaps they will, but only when public is taken in the context as in public utility or public city. But individuals are not going to buy a flow battery, it is a chemical plant.