What moves inside a rechargeable battery?

A rechargeable device can run again after charging because its cell restores an energy-storing chemical arrangement. In a common lithium-ion design, lithium enters and leaves graphite at the negative electrode and a different host at the positive electrode. Energy belongs to this whole arrangement, rather than to a tank of liquid lithium fuel.

During discharge, the coupled electrode reactions favor transferring lithium from the negative material to the positive material. Lithium ions move through the electrolyte inside the cell. Electrons take the external circuit through the device being powered. The voltage expresses an energy difference per unit charge, and the chemical changes supply energy as charge passes through the load.

Both routes matter. If electrons could not move externally, growing charge separation would quickly oppose further reaction. If ions could not move internally, local charge imbalance would also interrupt sustained discharge. A porous separator keeps the electrode solids from touching while electrolyte in its pores carries ions. It does not provide an internal wire for electrons.

Charging uses an external electrical supply to drive the net changes in the opposite direction. Lithium ions return toward graphite and electrons reach it through the external circuit. The supply does work to restore a higher-energy chemical arrangement, which can remain when the circuit is disconnected and later provide another discharge.

Reversing the main chemical changes does not undo every change inside a cell. Side reactions, structural changes and resistance consume energy and gradually affect performance; chemistry, temperature and operating conditions influence capacity and lifetime. The illustration traces separate ion and electron routes in a common design without calculating voltage, charge time or remaining usable energy.