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What Is a Supercapacitor?

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  • Written By: Nick Oza
  • Edited By: A. Joseph
  • Last Modified Date: 23 August 2014
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A supercapacitor is a tool offering very high electrical capacitance in a small package. Unlike conventional capacitors, supercapacitors do not have a dielectric, an electrical insulator that can be polarized with the application of an electric field. Instead, the plates of a supercapacitor are filled with two layers of the identical substance. This allows for separating the charge. Without the need for a dielectric, the plates are packed with a much larger surface area, resulting in high capacitance.

Other names for a supercapacitor are an electric double-layer capacitor, supercondenser, pseudocapacitor, electrochemical double layer capacitor and ultracapacitor. Supercapacitors have unusually high energy densities in comparison to regular capacitors. Storage of energy is by means of a static charge.

Similar to a lithium-ion capacitor, a supercapacitor has a positive cathode that employs activated carbon material. Charges are stored in an electric double layer. Development of the layer takes place at the interface between the electrolyte, which is the liquid medium through which electricity is conducted, and the carbon.

Materials used in making supercapacitors vary. Many are made from powdered, activated carbon. Various institutions have researched the possibility of using carbon nanotubes. Certain polymers as well as graphene, a material made of tightly packed carbon atoms, are also used for production.

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There are several advantages of supercapacitors relative to batteries. Having a long life with little wear and tear occurring over many cycles, supercapacitors also have a low cost per cycle, charge rapidly and use simple methods of charging. The disadvantages of supercapacitors relative to batteries are that they have low energy densities, holding less energy per unit of weight when compared to electrochemical batteries. Cells of supercapacitors also have low voltages, requiring them to be connected in series with other supercapacitors to obtain higher voltages.

Electrolytic capacitors tend to have a capacitance that is larger than other types of capacitors. One of the uses of high-capacity electrolytics, such as supercapacitors, is in electrically powered vehicles similar to rechargeable batteries. Combining a supercapacitor with a battery in a single unit creates an electric vehicle battery. Electric vehicle batteries are long lasting, less expensive and much more powerful than other technologies.

Hybrid vehicles and electric vehicles use a system of storing energy, which is rechargeable. The rechargeable electricity energy system, as it is commonly known, uses supercapacitors as its storage system. Flywheel energy storage, or the rotational energy of a flywheel, and rechargeable electric traction batteries are also used as storage systems.

Another use of supercapacitors is in self-powered equipment, which can be powered by human muscle. The mechanically powered flashlight, driven by a supercapacitor, is a promising alternative to rechargeable batteries for electricity storage. Other applications include enhancing performance for portable fuel cells, such as generators, and improving the handling of batteries.

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