How do batteries work?

A battery converts stored chemical energy into electrical energy. Inside are two electrodes — a negative anode and a positive cathode — separated by an electrolyte. Chemical reactions at the anode release electrons, which cannot travel through the electrolyte and instead flow out through the external circuit (powering your device) to reach the cathode, while ions move internally to balance the charge. This flow of electrons is the electric current. In rechargeable batteries like the lithium-ion cells in phones and electric cars, applying power reverses the reactions, restoring the chemicals to their original state so the battery can be used again — typically for hundreds to thousands of cycles.