Angew. Chem. Int. Ed. http://dx.doi.org/10.1002/anie.201103493 (2011)

Supercapacitors store electrical charge at electrode/electrolyte interfaces and can have much larger capacitances than conventional dielectric-based capacitors. The electrodes of these devices are usually made of carbon, and various nanostructures, including carbon nanotubes and graphene, have previously been employed. Such capacitors can operate at high charge and discharge rates for over a million cycles, but the energy they can store is usually significantly lower than that of batteries. Donglin Jiang and colleagues at the Institute for Molecular Science, Okazaki have now created supercapacitors with high energy densities using electrodes made from microporous polymers.

The polymers are composed of a network of fused benzene rings in which some of the carbon atoms have been replaced with nitrogen atoms, and have an extended π-conjugated system and nanopores with diameters of less than 2 nm. This conductive structure allows electrolyte ions to move into the pores and helps the electrostatic charge-separation layers to form. As a result, the polymer-based supercapacitors have specific capacitances higher than those of carbon-based devices and exhibit excellent performance stability. Furthermore, they have energy densities as high as 53 Wh kg−1, which is comparable to that of nickel-metal hydride batteries.