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. In their paper published in the journal Science, the team describes their process and how well the newly developed supercapacitors worked, and their goal of one day helping supercapacitors compete with batteries.
Like a battery, a capacitor is able to hold a charge, unlike a battery, however, it is able to be charged and discharged very quickly—the down side to capacitors is that they cannot hold nearly as much charge per kilogram as batteries.
Ref: Nitrogen-doped mesoporous carbon of extraordinary capacitance for electrochemical energy storage. Science (18 December 2015) | DOI: 10.1126/science.aab3798
Carbon-based supercapacitors can provide high electrical power, but they do not have sufficient energy density to directly compete with batteries. We found that a nitrogen-doped ordered mesoporous few-layer carbon has a capacitance of 855 farads per gram in aqueous electrolytes and can be bipolarly charged or discharged at a fast, carbon-like speed. The improvement mostly stems from robust redox reactions at nitrogen-associated defects that transform inert graphene-like layered carbon into an electrochemically active substance without affecting its electric conductivity. These bipolar aqueous-electrolyte electrochemical cells offer power densities and lifetimes similar to those of carbon-based supercapacitors and can store a specific energy of 41 watt-hours per kilogram (19.5 watt-hours per liter).