A couple years ago Tesla CEO Elon Musk said in an offhand remark that he thought capacitors — rather than batteries — might be the energy storage tech to deliver an important breakthrough for electric transportation. Tesla cars, of course, use lithium ion batteries for storing energy and providing power for their vehicles, but Musk is an engineer by nature, and he likes what ultracaps offer for electric cars: short bursts of high energy and very long life cycles. Capacitors are energy storage device like batteries, but they store energy in an electric field, instead of through a chemical reaction the way a battery does. A basic capacitor consists of two metal plates, or conductors, separated by an insulator, such as air or a film made of plastic or ceramic. During charging, electrons accumulate on one conductor, and depart from the other. Supercapacitors also have two metal plates, like capacitors, but they’re usually coated with a spongelike, porous material known as activated carbon. The porous material makes the surface area a lot larger and boosts the energy density. They’re also immersed in an electrolyte made of positive and negative ions dissolved in a solvent. Finally, each of the ultracapacitor’s carbon electrodes ends up having two layers of charge coating its surface. Ultracapacitors and supercapacitors are often used interchangeably to mean the same thing — basically, a double-layer capacitor. via Gigaom.