What type of energy is stored in a battery?

A battery stores chemical energy, which it converts into electrical energy when connected to a circuit.

Inside a battery, chemical reactions at the anode and cathode create a difference in electric potential. When the circuit is closed, electrons flow through the external wire while ions move through the electrolyte inside the battery. This controlled redox reaction releases energy that can power a device.

Alessandro Volta created the first true battery, the voltaic pile, around 1800. Modern batteries use many chemistries, including alkaline, lead–acid, lithium-ion, and nickel-metal hydride. Rechargeable batteries store chemical energy again when an external electrical current reverses their chemical reactions.

A common mix-up is calling the stored energy electrical energy. Electricity is the useful output during discharge; the battery’s primary stored form is chemical energy. Some energy is also lost as heat, which is why batteries can warm during heavy use or charging.