Furthermore, the cars are not plug-in hybrids, all electricity generation comes from regenerative braking.
What is regenerative braking? Never heard of this term before. If the electricity is generated while driving itself, then the need for an invertor is eliminated. Also, a cheaper battery will do the trick, instead of an expensive one made out of Lithium and Cobalt.
When the car slows down, the electric motor starts working as an electric generator by transforming the kinetic energy of the moving car into the electric energy, thereby recharging the battery. Cheaper battery means that it will be made from, for example, plumbum, but it is heavy and not very suitable for passenger cars. Lithium is the lightest of metals (excluding metallic hydrogen and helium), so its choice is quite justified
In fact, it is lighter than water (almost twice)