Before lithium batteries started to be manufactured, they were already fantasizing about being able to make lithium batteries. The reason is that lithium is a metal that has a tendency to detach from its outermost electron. After all, electricity is the transit of electrons, so to produce electricity we need substances that tend to detach from them.
Lithium is the metal with the lowest reduction potential (-3.05V). This means that it is the chemical element that has more tendency to give away electrons. When you give away your outermost electron, lithium becomes positively charged. We represent it as Li + and call it lithium ion. Hence, lithium batteries are also called lithium ion batteries.
That lithium gives up electrons with such joy is obviously a plus, but at the same time it’s a curse. Give electrons to anyone. To the air, to the water, to everything. This means that it is a very unstable metal, which quickly oxidizes on contact with air, and reacts violently on contact with water. That is the reason why the history of lithium ion battery has not been a smooth journey.
The batteries all have the same fundamental scheme:
– Anode or negative electrode. This is where some substance breaks off electrons. We call these electron loss reactions oxidation reactions. By agreement, when representing batteries, the anode is drawn to the left.
– Positive cathode or electrode. This is where some substance accepts the electrons. We call these electron capture reactions reduction reactions. It is the reverse reaction to oxidation. By convention, when representing batteries, the cathode is drawn on the right.
– Electrolyte. The electrolyte acts as a separator between the cathode and the anode. It serves to maintain the balance between the charges of the anode and the cathode, since, if the electrons flow from anode to cathode, a potential difference occurs, something like a decompensation of charges, which stops the flow of more electrons. The electrolyte allows the flow of ions (not of electrons) that rebalance the charge between both sides.
– The anode and cathode are attached to the battery by means of the electrolyte. They are also joined on the outside by an external conductor through which only electrons circulate. The conductor has two ends, positive pole and negative pole, like any battery. So lithium ions flow from one end to the other, and electrons flow through the outer conductor.
In rechargeable batteries the oxidation (give up electrons) and reduction (capture electrons) reactions are reversible, they can flow in both directions. Some products like Large Lifepo4 Battery apply the principle.
The most common current lithium ion batteries have a cobalt oxide cathode and an anode of a graphite-like material called coke. Both the cathode and the anode have a layered arrangement in which they can house lithium. Lithium will travel from cathode to anode or anode to cathode through the electrolyte depending on the charge or discharge cycle. Instead, the electrons will circulate through an external circuit.