How does a battery work?

A battery is a device that converts stored chemical energy into electrical energy. Inside, it has two electrodes, a negative one called the anode and a positive one called the cathode, separated by a chemical substance called the electrolyte. When the battery is connected in a circuit, a chemical reaction at the anode releases electrons, which cannot pass through the electrolyte and so are forced to travel through the external wire to reach the cathode, creating an electric current that can power devices. Meanwhile, charged particles called ions move through the electrolyte inside the battery to balance the flow. In disposable batteries, the reaction eventually uses up the chemicals and the battery dies, while rechargeable batteries, like the lithium-ion cells in phones, can reverse the reaction when charged. The first true battery was invented by Alessandro Volta in 1800.