MIT scientists plan to replace the activated carbon of current ultracapacitors, which can can store more charge than a capacitor, with a dense, microscopic forest of carbon nanotubes grown directly on the surface of the current collector.

This would create a device that can hold up to 50 percent as much electrical energy as a comparably sized battery, while being more effective at rapid, regenerative energy storage than chemical batteries and with longer life.

This feat would allow ultracapacitors to supplant batteries in a number of mainstream applications.