Electrolyte
Rechargeable batteries - Theoretical considerations

We're going to start by looking at the electrolyte, which supports ionic conduction, without which the electric current couldn't flow inside a battery. Generally liquid, in most batteries (Li-ion, Pb-acid, Ni-MH...), the electrolyte can also be solid, as in so-called all-solid lithium batteries or in batteries operating at high temperatures (Na-FeCl ₂ , Na-NiCl ₂ , Na-S...). To fully understand how it works, we need to look at the interactions of the ions with the solvent and of the ions with each other, the chemical reactions giving rise to them and their transport in solution.