ULTRA CAPACITORS

ULTRA CAPACITORS

ULTRA CAPACITORS ARE ALSO CALLED AS SUPER CAPACITORS or ELECTRIC DOUBLE LAYER CAPACITOR (EDLC) or ELECTROCHEMICAL SUPERCAPACITOR .

Ultra capacitors are a type of electrical component that are capable of holding electrical charge nearly 10,000 times more than a standard electrolytic capacitor. They have the highest available capacitance values per unit area and the greatest energy density of all capacitors.

An ultra capacitor differs fundamentally in it’s internal structure . Instead of two electrodes separated by an insulating layer, ultra capacitor use a porous medium that produces the effect of a pair of gigantic surface area.

As a result, the ultra capacitor has far more capacitance than any conventional high capacitance component.

The capacitance values of an ultra capacitor is determined by two stage principal (1) Double layer capacitor (2) Pseudo capacitance,Both of which contribute to the total capacitance of the capacitor.

Materials used in ultra capacitors

Electrodes for EDLC(1) Activated Carbon(2) Carbon Aerogels(3) Carbon Nanotubes (1)Activated carbon

It was the first material chosen for ELDC electrodes. It is porous and with high specific surface area.in bulk it form a low density with many holes and it is less expensive.(2)Carbon aerogelsCarbon aerogels are formed from continuous network of conductive carbon nanoparticles with interspersed mesomers . It bond chemically to the current collector it does not need additional adhesive binding agent.(3)Carbon nanotubesCarbon nanotubes in ultra capacitors can greatly improve and enhance the performance of electrochemical capacitors.

Electrodes for Pseudo Capacitors(1) Conducting polymer(2) Metal oxides

(1)Conducting polymerConducting polymer have high capacitance and conductivity. Such polymer include polyanilene, polypyrrole, and polyacethylene. And the cost is low compared to carbon based electrode material.(2)Metal oxideMetal oxide has explored as electrodes for pseudo capacitors because of their high conductivity. Many metals like ruthenium, iron, iridium and sulphides like titanium sulphide and their combinations are used. Ruthenium dioxide with combination with sulphuric acid

electrolyte is one of the best example of pseudo capacitance.

Electrodes for hybrid capacitors

(1)Composite(2)Assymetric(3)Battery type

(1)CompositeComposite electrode integrate carbon material with conducting polymer or metal oxide and incorporate both physical and chemical charge in a single electrode.(2)AssymetricAssymetric hybrid, combine faradaic and non faradaic process by coupling ELDC electrode with pseudo capacitor electrode.

(3) Battery type

Like asymetric hybrids, battery-type hybrids couple two different electrodes.Electrodes in hybrid super capacitors include nickel hydroxide, lead oxide and LTO as anode and activated carbon as the cathode with a lithium salt in an organic solvent electrolyte. Battery type hybrid are unique in coupling a super capacitor with a battery electrode.This specialized configuration reflects the demand for higher energy super capacitors and high power batteries.