How do lithium-ion batteries work?

The most common type of electric vehicle battery is called a ‘lithium-ion ‘ battery. Lizzie Driscoll, from the University of Birmingham, invites us to liken the inner workings of a battery to that addictive party game “Jenga”, where you take turns to dislodge wooden blocks from a progressively more precariously balanced tower...

Lizzie - I want you to picture two towers of Jenga blocks built up. These are our electrodes inside the battery, and in our example, they are built up of several different elements. In one Jenga tower, we have blocks made of cobalt and lithium arranged in alternating layers. The other Jenga tower is made up of only carbon blocks, and the tower has conspicuous gaps where blocks are missing. When we charge a battery like this and pump energy into the system, the lithium blocks get pulled out of the first Jenga tower and slot into those gaps in the second tower. After some time, all the lithium blocks fill up all the gaps to make a full Jenga tower of carbon and lithium, and because it took energy to make that carbon-lithium tower, energy is stored up in the structure. When we then use the battery, the lithium blocks move back into the first Jenga tower, releasing energy that we harness to power our electric vehicles, for example. If the lithium blocks are being taken out of the cobalt tower too slowly it will take a long time to charge our battery, but if we take them out too quickly, well, we all know what can happen with Jenga! The towers will collapse and be of no use at all. So we need to find a good balance of speed when charging. Finally, imagine you’re repeating this process of moving blocks between Jenga towers over and over again - the towers aren’t going to remain in perfect shape. This is what battery degradation looks like, and why all batteries ultimately will only last so long...much like a Jenga tower in my house!