Ultracapacitors to Boost the Range of Electric Cars

ultracapacitor technology could make electric cars cheaper and extend their range. The company, based in Mountain View, California, has developed a way to make electrodes that results in ultracapacitors with five to seven times as much storage capacity as conventional ones.
Conventional ultracapacitors, which have the advantage of delivering fast bursts of power and can be recharged hundreds of thousands of times without losing much capacity, are too expensive and store too little energy to replace batteries.

Using a conventional electrolyte, the company has demonstrated energy storage of 20 watt-hours per kilogram, as opposed to roughly five watt-hours for a conventional ultracapacitor. Using a more expensive ionic-liquid electrolyte, it has made ultracapacitors that store 35 watt-hours per kilogram.
Part of the reason battery systems are so expensive and bulky is that the batteries degrade as they're used, especially when exposed to extreme temperatures—so automakers often augment them with cooling and heating systems, and add extra battery cells to offset losses in performance over time. Ultracapacitors could sidestep this problem, because they can be recharged without degrading and can work well in a wide range of temperatures.