supercapacitor otherwise ultracapacitor; electric double-layer capacitor (rus. суперконденсатор otherwise ионистор; супер-конденсатор; ультра-конденсатор) — capacitor to accumulate the energy (charge) as a bound charge (electric double layer) in thin adsorption mono- and polymolecular layers (films) at the electrode-electrolyte interface.

Description

Electrodes of a supercapacitor that accumulate the charge in the double electric layer on interfacial area of the electrode and the electrolyte, should have a highly developed surface, of about 1,000 m2/g and higher, to ensure the practice-relevant specific energy. In this connection carbon porous materials are used as supercapacitor electrodes (activated carbon, carbon cloth, etc.). However, carbon electrodes have high electrical resistivity and high resistance of electric feeder contacts. In addition, such electrodes, when operating with an aqueous electrolyte, have an operating voltage limit of less than 1V, because irreversible electrochemical reactions are possible at high voltages and they can lead to disruption in the fine structure of carbon materials and shorten the electrodes' service life drastically. Organic and solid electrolytes can help increase the operating voltage to 3V, but at the cost of reduced conductivity of the electrolyte, and thus, increased internal capacitor resistance and decreased power density.

Supercapacitors have several advantages over conventional electrochemical power sources, such as galvanic cells and accumulators:

-they are fast to charge and discharge;

-low degradation even after hundreds of thousands of charge / discharge cycles;

-light weight;

-low-toxic materials;

-high efficiency (more than 95%);

-non-polarity (although EDLC have "+" and a "-" markers, they are done just to denote the polarity of residual voltage after the capacitor is charged by the vendor).

The disadvantages of supercapacitors:

-the specific energy (1-10 W · h/kg) is lower than the one of the standard batteries (> 20 W · h/kg);

-the voltage depends on the charge;

-internal contacts can burn out due to short-circuits;

-high self-discharge;

-low voltage, short service life (hundreds of hours) at the limit voltage of the charge.

To overcome some of the above, electrochemical supercapacitors have been developed to combine the advantages of chemical power sources and supercapacitors.

Illustrations

Comparison of structural diagrams of three capacitors. On the left:
Comparison of structural diagrams of three capacitors. On the left: "common" capacitor; in the middle: electrolytic capacitor; on the right: ultracapacitor.

Authors

  • Razumovsky Alexey S.
  • Tolkachev Nikolay N.

Source

  1. Electric double-layer capacitor // Wikipedia, the free encyclopedia. — http://en.wikipedia.org/wiki/Electric_double-layer_capacitor (reference date: 01.08.2010).

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