How do batteries store energy?

A battery stores energy in chemical form and converts it into electrical energy through reactions between its two electrodes and an electrolyte. When a battery is connected in a circuit, a chemical reaction at one electrode releases electrons that flow through the external wire to the other electrode, producing an electric current, while ions move through the internal electrolyte to balance the charge. In rechargeable batteries such as lithium-ion, applying external power drives the reactions in reverse, restoring the chemical state so the battery can be used again. The voltage a battery produces depends on the specific materials used for its electrodes.