All material consists of atoms, the smallest items with a chemically stable nature. They usually contain an equal number of positive protons and negative electrons. However, in some cases the numbers are out of balance, and the atoms have a positive or negative charge. We describe the role of ions in lithium ion batteries.
Energy from Ions in Lithium Ion Batteries
Lithium ion batteries power more and more of our electronic devices each day. They also play a key role in utility energy storage. Yet each of them, from button- to container-size relies on five critical components. These are an anode, a cathode, a separator, an electrolyte, and a pair of current collectors.
The anode and the cathode store the active material. The electrolyte allows the positive ions in lithium ion batteries to shuttle between the anode and cathode via the separator. While the direction in which they travel depends on whether the battery is charging or discharging.
A parallel event occurs while the battery discharges. The movement of the ions causes free electrons to accumulate at the positive current collector. They have to go somewhere but the separator prevents them from moving internally. And so they follow the line of least resistance through an available external circuit.
This Flow Reverses During Recharging
We described the process while the battery discharges. However, there are a limited number of positive ions in lithium ion batteries. When they are used up, the battery is flat unless we replenish it. That is, send the ions back to where they came from (if the design allows it).
Lithium-ion batteries may be replenished by connecting a suitable supply to the current collectors. This reverses the flow of electrons, causing the ions to follow suit to restore the balance. When this is complete, the lithium battery is almost as good as new again.
More Information
Passivation on Negative Battery Electrodes
