Cars are unlikely to have huge supercapacitors useful for changing the charge much, too. (And there's not much point in moving power stored in a capacitor to be stored in a battery).
The main use of this is to provide short duration power, as you describe. That is, lithium batteries have great energy density but not as great power density or cycle life as capacitors. So a small amount of bulk capacitance can improve battery performance and reduce stresses on the battery.
This is more useful for short range vehicles like plug-in hybrids, because they have smaller packs. Larger vehicle packs tend to have plenty of power available, as a side effect of being designed to store tons of energy.
Even for high discharge I'm skeptical, lithium titanate batteries are probably much better, their durability and extreme charging and discharge rates make them half way to capacitors already.
You could say that. You could also be more pedantic and say that this comes at the cost of some decrease in battery life (and efficiency) due to the resistance resulting in some amount of heat in order to facilitate this high-speed charging process.
But I don’t know if the ROI on improved battery life would be worth the complexity, size, weight, and cost of a two-stage charging process. As battery tech improves, that resistance continues to come down.
What does? I said the limitation is usually getting enough electricity to charge them fast. Most of the time EVs are not being charged as fast as they could be.
The traces supplying power aren't theoretical, so they have a nonzero impedance. This means that when there is any change in power demand due to transistors switching, the trace will try to resist this change in supply current. An increased power demand leads to a very local voltage drop, a reduced power demand leads to a very local voltage spike.
Bypass capacitors are placed as close as possible to the individual chips to reduce the impedance between the capacitor and the chip. You even intentionally use smaller capacitors because the bigger ones have a higher impedance.
Without bypass capacitors every sudden draw of power would pull the supply voltage of the whole system down, especially if your power source (battery) can't react that quickly or has limited discharge rates.
Without having looked into the plans here, I'd expect a super-capacitor solution to look like this:
1. You charge your cars of super-capacitors super quickly at special charging spots and drive away
2. The stored charge is then partly used for driving, partly used to charge the cars actual battery and partly used to act as a bypass capacitor to smooth out the load for the battery
3. Eventually the capacitors are empty, but you had a short charging process that filled part of your batteries