How do electrons and ions follow different routes in a discharging cell?

A discharging battery converts available chemical energy into electrical work through coupled electrochemical reactions. An electrochemical cell separates these reactions so that electrons can pass through an external circuit and supply a load. The illustration represents a specific ideal copper–silver galvanic cell, a cell whose spontaneous overall reaction can drive current. It is a route diagram, not a description of every battery chemistry.

At the copper anode, copper atoms lose electrons and enter solution as copper ions. Loss of electrons is oxidation. At the silver cathode, silver ions gain electrons and become silver metal; gain of electrons is reduction. During discharge in this cell, the anode is negative and the cathode positive. Electrons move through the external wire from the copper anode, through the load, to the silver cathode.

The internal route is different. Ions in the solutions and ion bridge carry charge; free electrons do not travel through the electrolyte from one electrode to the other. As positive copper ions accumulate near the anode, bridge anions move toward that side. As silver ions are removed near the cathode, bridge cations move toward the cathode side. This ionic response helps prevent a growing charge imbalance from stopping the reaction.

A sustained discharge therefore needs a connected electron path, an internal ionic path, and reactants with available chemical driving energy. Opening the external path stops sustained current even though a potential difference may remain. Reactant depletion can also stop useful discharge. The electrical energy is supplied by the overall chemical change, not created by circulating electrons.