Super capacitors
Ultra capacitors or super capacitors are electrochemical systems that store energy within their double-layered structure consisting of opposite charged materials. Electrodes made from activated or porous carbon are used in the production of the highest rated super capacitors. Although this provides a high storage capacity, it slows down the rate at which charging and discharging occurs.
Carbon onions
The integration of carbon onions has opened new horizons in the use of micro-scale energy storage for applications for which conventional electrolytic capacitors are not sufficient. The use of onion-like carbons (OLC) in the development of micro-super capacitors now seems to be a promising venture.
A team of researchers made a capacitor using onion-like shells of graphene for electrodes to get enhanced energy and power densities.
Although their surface area is rather low compared to the surface of the activated carbons, it has qualitative value, since it is fully accessible to the electric charges. The team began with creating an exposed electrode out of OLC. The OLC (at 6-7 nm diameters) could adhere onto the electrode without any binding agent or polymer separator making the process easier.
The rate of charge and discharge and power density of batteries using OLC was very high compared to the activated carbon capacitor and thin film lithium battery.