A quick idea after watching Search for the Super Battery NOVA Documentary on youtube.
Philosophically its possible to have one electrode ?much bigger than the other. The idea is to have an over supply of ions between them.
Since I believe coal is much less heavy than the positive electrode. Then what if you make the coal ”apartment” oversized for the transferable amount of ions.
The idea is to let the ions select among themselves a lot more since there are many more of them. A lot more apartments to select from. This would not be the case if every single one of the ions were to be used. Could be some efficiency gain here perhaps?