Interestingly it seems to have some applications for high peak power and regen, they had a car in the Dakar rally:

https://www.jtekt.co.jp/e/products/capacitor/capacitor_mobil...

https://www.jtekt.co.jp/e/engineering-journal/assets/1019/10...

You would use these to provide peak power in a system that had short term power needs that were high above the average power needs AND had that power requirement as a bottleneck. Energy is the bottleneck for cars though, not power. unless you're wanting your prius to accelerate like a ferrari

Maybe it would be useful for less losses with regenerative braking? These would presumably be able to charge much faster and then trickle that power out to the normal battery. You'd need actual power numbers for a car to determine if it would be useful or not.

In other words this is for "boy I wish I didn't have to have so much extra battery capacity in order to get the power I need" situation which... cars don't have. Maybe in F1?

Regen braking,