A team of researchers working in China has found a way to dramatically improve the energy storage capacity of supercapacitors by doping carbon tubes with nitrogen. The researchers achieved a threefold increase in the amount of charge that can be held by supercapacitors, noting also that that their supercapacitor was capable of storing 41 watt-hours per kilogram and could deliver 26 kilowatts per kilogram to a device.
Like a battery, a capacitor is able to hold a charge. Unlike a battery, however, it is charged and discharged very quickly. The down side to capacitors is that they cannot hold nearly as much charge per kilogram as batteries. Supercapacitors are capacitors that have much higher capacitance than standard capacitors and they generally employ carbon-based electrodes.
The new supercapacitor was made by first forming a template made of tubes of silica. The team then covered the inside of the tubes with carbon using chemical vapor deposition and then etched away the silica, leaving just the carbon tubes, each approximately 4 to 6 nanometers in length. Then, the carbon tubes were doped with nitrogen atoms. Electrodes were made from the resulting material by pressing it in powder form into a graphene foam.
The researchers report that the doping aided in chemical reactions within the supercapacitor without causing any changes to its electrical conductivity, which meant that it was still able to charge and discharge as quickly as conventional supercapcitors. The only difference was the dramatically increased storage capacity.
Because of the huge increase in storage capacity, the team believes they are on the path to building a supercapacitor able to compete directly with batteries, perhaps even lithium-ion batteries. They note that would mean being able to charge a phone in mere seconds. But before that can happen, the team is looking to industrialise their current new supercapacitor, to allow for its use in actual devices.