How Does a Lithium-Ion Battery Charge and Discharge?

A lithium-ion battery has three main components: a cathode (positive electrode, typically lithium cobalt oxide or lithium iron phosphate), an anode (negative electrode, usually graphite), and a liquid electrolyte with dissolved lithium salts. During charging, an external voltage drives lithium ions from the cathode through the electrolyte to intercalate (insert) into the graphite anode; electrons flow through the external circuit. During discharge, the process reverses: lithium ions spontaneously migrate back to the cathode, and electrons flow through the external circuit to power the device. This "rocking chair" mechanism is highly reversible, allowing 500–1,000+ charge cycles. Energy density ranges from 150–265 Wh/kg, far exceeding lead-acid or nickel-metal hydride batteries.