How does a lithium-ion battery work?

- Jun 01, 2018-

First, we need to look at how a lithium-ion battery works in general. Like any other battery, its basic design sees an electrolyte (the “transport medium”) ferrying lithium ions back and forth between the negative electrode and the positive electrode. In a totally discharged batteries, our mobile lithium ions will be entirely connected to the positive electrode — their chemical properties keep them bound to the positive electrode material while they lack electrons. If we give them electrons by pumping electricity into the system (recharging), they will naturally dissociate from the positive electrode and migrate back to the negative electrode. Once they’re all lined up on the other side, loaded with nice high-energy electrons, we call the battery “charged.”

This stable state breaks down when we provide an avenue for the electrons now trapped at the negative electrode to travel down their charge gradient to the positive side of the battery — this takes away electrons from lithium in the negative electrode and makes them again Li+, causing them to naturally migrate all the way back. We can use that negative-to-positive electron flow to power everything from pacemakers to electric cars, and it all ultimately comes down to the back-and-forth movements of ions. Incidentally, it’s only recently that scientists have discovered exactly why too many back-and-forth reactions cause a battery to slowly die.