When a lithium-ion battery (graphite anode, LiCoO₂ cathode) discharges, which correctly describes the movement of lithium ions and electrons?

Answer: A. Li⁺ moves through the electrolyte from the negative electrode to the positive electrode, and electrons flow through the external circuit from the negative electrode to the positive electrode

On discharge, lithium stored between the graphite layers splits into Li⁺ and an electron and leaves the negative electrode. Li⁺ moves through the electrolyte (and separator) to the positive electrode and enters between the layers of LiCoO₂, while the electrons flow through the external circuit to the positive electrode as well, doing work on the way. Electrons flow from the negative to the positive electrode, so the current flows from positive to negative; the choice with electrons flowing from positive to negative confuses the direction of current with the flow of electrons. The choice with Li⁺ moving from positive to negative gives the direction of Li⁺ during charging: on charge, an external power supply pushes electrons into the negative electrode and Li⁺ also returns from the positive to the negative electrode. On both discharge and charge, Li⁺ and electrons move in the same direction, keeping the charge on both electrodes balanced. Because Li⁺ simply shuttles between the electrodes while the electrode frameworks are preserved, it is also called a rocking-chair battery.