Capacitors and ultracapacitors

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See also Batteries Capacitors and Ultracapacitors Flywheels Hydroelectric Energy. 

Burke AF, Miller M. Characteristics and Applications of Advanced Ultracapacitors. Proceedings of the 12th International Seminar on Double Layer Capacitors and Similar Energy Storage Devices, Deerfield Beach, Florida, USA, Dec. 9-11, 2002. 

The double-layer capacitor is one of the electrochemical capacitors showing intermediate performances between conventional capacitors and rechargeable batteries from the viewpoint of energy and power densities. Although the terms supercapacitor and ultracapacitor are often used for double-layer capacitors, in a sense that they have higher capacitance than conventional capacitors (ceramic, film, aluminum electrolytic, or tantalum electrolytic capacitors), these terms are not to be used because they are the trademarks of certain companies products. 

An electrochemical capacitor differs from a conventional electrostatic capacitor in that the energy is stored in the form of ions rather than electrons. This results in an increase in the amount of energy that is stored at the expense of reduced power output per unit mass/volume. Thus, an electrochemical capacitor begins to assume some of the characteristics of a rechargeable battery. Such devices are variously referred to as supercapacitors and ultracapacitors . Since there is some confusion over the distinction, we prefer to use the generic term electrochemical capacitor . 

The terms supercapacitor and ultracapacitor are used to describe any double layer or redox capacitor with specific energy and specific power intermediate to batteries and traditional capacitors. Typically, ultracapacitor refers to a device comprised of two carbonaceous electrodes whereas supercapacitor refers to a similar device in which the two carbonaceous electrodes are catalyzed with metal oxides such as Ru02. This chapter will use the term supercapacitor to describe EAP-based capacitors, since that seems to be the most commonly used term for such materials. Another charge storage configuration uses an EAP electrode and a battery-type carbonaceous electrode in what is known as a hybrid device (however, outside of the EAP-based supercapacitor field, hybrid may refer to the combination of a battery electrode such as nickel hydroxide with a carbon electrode) [1]. 

In the field of power capacitors the company claims that its portfolio is number one worldwide with its rugged range of aluminium models able to withstand the high ambient temperatures of car engine compartments. Epcos also makes film capacitors, where the plastic film may be up to ten times thinner than a human hair, and ultracapacitors. The capacitor division also supplies power factor correction modules as a cost saving service to customers. 

It follows from these data that the (theoretical) specific capacity of the active materials of such a double-layer capacitor may attain 100 F/g. This is many orders of magnitude above the values characterizing other capacitor types (film and electrolytic). For this reason such capacitors have also become known as super- or ultracapacitors. 

A classic definition of electrochemical ultracapacitors or supercapacitors summarizes them as devices, which store electrical energy via charge in the electrical double layer, mainly by electrostatic forces, without phase transformation in the electrode materials. Most commercially available capacitors consist of two high surface area carbon electrodes with graphitic or soot-like material as electrical conductivity enhancement additives. Chapter 1 of this volume contains seven papers with overview presentations, and development reports, as related to new carbon materials for this emerging segment of the energy market. 

An electrochemical capacitor is a device that stores electrical energy in the electrical double layer that forms at the interface between an electrolytic solution and an electronic conductor. The term applies to charged carbon—carbon systems as well as carbon-battery electrode and conducting polymer electrode combinations sometimes called ultracapacitors, supercapacitors, or hybrid capacitors. 

In recent years there has been increasing interest in the power capacitors, ultracapacitors or supercapacitors based on electrochemical systems. These include electric double layer capacitor (EDLC) types based on carbon electrodes with suitable electrolyte systems, and electrochemical capacitors with pseudocapacitance [34,35],... 

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