Basically, you have two foils coated with conductive material, most likely copper on the positive side and aluminum on the negative side, with a microporous separator in between, which not only, as the name suggests, keeps separate the two foils, plus and minus pole, but also restricts the passage of certain materials. Another insulating layer is needed underneath this structure, so to speak, to prevent contact and short circuits, e.g. when winding up.

Lithium is the element after which the battery is actually named. It's already incredibly light on its own, and you only need very little of it. In fact, it is the only element of a battery that moves from the positive electrode to the negative and then back again. There it is not waiting on the surface for the next charging or discharging, but according to Wikipedia is 'bound in the host lattice of a carrier material'.

You can easily calculate the amount of lithium you need yourself if you assume a currently favorable value of 80 grams per kWh for pure lithium. We always take the big Audi, in which the 90 kWh battery weighs 700 kg, then we would have a good 11 percent Lithium content in relation to the entire battery. It's just the lightest solid element at all. In addition, it is very reactive, so that it can be dangerous for humans especially in connection with the skin (moisture).

Although it's called separator, it lets the lithium ions pass in both directions. Although lithium is very unstable on its own, it arranges itself but stably on the plus side within the structure of a metal oxide as a host lattice. Movements occur when we plug in a charger. In principle, the lithium on the positive side is separated into its electron and the remaining, now negatively charged, rest of the atom. While the former passes externally through the charger and only then hits the negative side, the residual atom, also known as the lithium ion, moves directly there through the separator, attracted by it.

A prerequisite for this internal movement is currently a liquid electrolyte, which is then given before the airtight seal between the separator and the two foils. A solid electrolyte is seen as a milestone in battery development, but it has not yet found its way into series production. In the end, lithium ions and electrons are found in the loose and rather porous graphite layers on the negative side and are embedded there.

So the charger performs the function of a kind of pump that brings the negative side to a higher energy level. All you need for the way back is an external cable connection, of course without a charger, but if possible with a consumer, otherwise a short circuit will occur. The current flow comes about through the attraction of the positive side on the negative electrons. The higher energy level of the minus side is brought back into line with the plus side. The positive lithium ions, attracted by the increasingly negative plus side, begin their way back.

A very important issue with this battery seems to be the respective embedding of the lithium after return and possible difficulties to leave the positive side again when charging. An aggregation of lithium ion and its only electron on the outer shell is probably not necessary, because the electrons come together in metal lattices to form point clouds. What is astonishing is that the materials are most likely to change when talking about a new variant of the lithium-ion battery, not the negative side or the electrolyte.

Battery research, in which e.g. the federal government is investing heavily at the moment, now has the task of varying the individual mixtures of the electrolyte and the negative side and then testing the effect. Since the combination of the individual parts alone results in an improbably large number of samples, only very small button cells are built and these are also built with robot technology if possible.

In addition to the difficulties in development, there are almost even greater difficulties in testing. Because it is by no means just the confirmation of the function immediately after assembly, but rather even more important long-term tests over maybe half a year or more with a constant change of charging and discharging. For example, the cycle stability of the battery is tested, which is very important for the later use of a battery with this basic structure in a car.

If possible, this all happens over 24 hours a day and the summary of the data, which then allows new conclusions for battery research, is already attributed to the somewhat vaguely defined artificial intelligence. Perhaps the term 'machine learning' is more appropriate here.