Question About Lithium-Ion Battery Fundamentals

Thread Starter

Baba Ram Dass

Joined Dec 17, 2015
Hello all, new member to the forums here. I have some questions about the migration of lithium ions during discharge and recharge of lithium-ion batteries.

1) Say we are looking at a fully charged lithium-ion battery; the anode is graphite and fully saturated with lithium atoms in their reduced form and the cathode is cobalt oxide ready to uptake lithium ions. The lithium atoms oxidize and release their electrons to the circuit while migrating across to re-complex with said electrons in the cobalt oxide cathode. What causes this process to initiate and continue? Is it simply an equilibrium based phenomenon where the lithium wants to flow across the cell due to a concentration gradient? If so, wouldn't this process slow down as the magnitude of the gradient is reduced, causing the battery to put out progressively less power over time?

2) Secondly, what exactly is happening when you plug in a phone, for example, that is causing this flow to be reversed and restoring the initial graphite-lithium complex? Is the circuit modulated such that current can only flow in one direction until it is plugged in, which reverses the allowed direction?

Sorry, I know there are a lot of questions. Electronics have never been particularly intuitive to me and I cannot seem to find any information on the interwebs with the detail I am seeking.