What is a battery?
Batteries power our lives by transforming energy from one type to another.
Whether a traditional disposable battery (e.g. AA) or a rechargeable lithium-ion battery (used in cell phones, laptops and cars), a battery stores chemical energy and releases electrical energy.
There are four key parts in a battery — the cathode (positive side of the battery), the anode (negative side of the battery), a separator that prevents contact between the cathode and anode and a chemical solution known as an electrolyte that allows the flow of electrical charge between the cathode and anode.
Lithium-ion batteries that power cell phones, for example, typically consist of a cathode made of cobalt, manganese, and nickel oxides and an anode made out of graphite, the same material found in many pencils. The cathode and anode store the lithium.
When a lithium-ion battery is turned on, positively charged particles of lithium (ions) move through the electrolyte from the anode to cathode. Chemical reactions occur that generate electrons and convert stored chemical energy in the battery to electrical current.
When you plug in your cell phone to charge the lithium-ion battery, the chemical reactions go in reverse: the lithium ions move back from the cathode to the anode.
As long as lithium ions shuttle back and forth between the anode and cathode, there is a constant flow of electrons. This provides the energy to keep your devices running. Since this cycle can be repeated hundreds of times, this type of battery is rechargeable.