The service of the battery is in other words the process of discharging, during which oxidation reaction happens at the negative electrode thus deliver electrons, while reduction reaction happens at the positive electrode thus receive electrons through external circuit. Thereby, electric current flows from the positive electrode to the negative electrode through external circuit correspondingly.

Electrolyte plays the role of ion conductor, through which the ions migration directionally and conduct (the cations migrate to the positive electrode, while the anions migrate to the negative electrode).

The external electron system and the inner-battery electrolyte ion system form a complete discharging system, thereby generating and delivering electrical energy.