There is an explanation of how a battery works that says that inside the battery, the electrons do a complete loop and can return to their starting point. When the electrons arrive in the positive terminal and they lost all of their potential energy, the battery does work on the electrons to put them back in the negative terminal so they are full of energy and reenter the circuit.
This explanation is very great because it answers questions : why does putting 2 batteries in series double the voltage? (because work has to be done two times on the electrons in the battery, so the potential energy doubles). Why connecting - of battery 1 to + of battery 2 without connecting + of battery 1 to - of battery 2 doesn't create electricity (because the electrons have to do a complete loop in the circuit and return to their starting point to make electricity for a long time. There is no external wire connecting - of battery 2 to + of battery 1 so there isn't a complete loop).
However, from what I understand of batteries, there is no electron that moves from the positive terminal to the negative terminal of the battery. The electrons of the circuit all come from the negative terminal and once they reach positive terminal there is nothing else happening except making the electrolyte ions neutral. They don't return to their starting point.
So could someone prove to me that inside a battery, electrons from the positive terminal are done work on and go to the negative terminal.
Or if this theory is false, could someone answer the two questions above that are easily answered by this theory in another way?