Any information about how heavy these will be and how these compare with lithium batteries?

if the device has the same energy density and lifespan as that of Lead-Acid Battery. Then what is so special about this supercapacitor device?

Close to instant charge and discharge meaning they could buffer a cheaper low C rated battery pack to run say a car. Have a phone or laptop with a few second charge. The energy density is related to size not weight in the article, they would most likely be considerably lighter as there is no lead.

Yes, this is the way forward, no question. Capacitors with sufficient energy density are, far and away, the most logical energy storage/release devices for the coming electric world. 5-second recharge times combined with relative safety, low weight and compact form factors is exactly what the real world is looking for.
Much rather have low cost Capacitors than expensive, heavy and volatile L-ion or Lipo batteries.

It charges in seconds not hours.

These capacitors are extremely dangerous as anyone who has short circuited an ordinary electrolytic capacitor.
All the energy released in about a millisecond would cause a massive explosion.
People seem to forget the exponential discharge curve of capacitors making them useless as normal batteries.

This is not for a car or motorbike. But the industrial implication for energy generation efficiency are tremendous.

What decays in a capacitor that would make it only last as long as a regular battery?

If these were used in an all-electric vehicle, could there be multiple alternators installed that would keep these constently charged when driving? Never need to refuel. That would be awesome.

I need this development for my rc airplanes.