Pseudocapacitor

Such processes are referred to as pseudofaradaic, and the capacity that corresponds to the surface processes is referred to as pseudocapacity. Capacitors built according to this principle are known as pseudocapacitors. 

Detailed studies have been performed on pseudocapacitors with layers of hydrated ruthenium oxide, RuOj- HjO. Protons relatively readily undergo intercalation and deintercalation in this material ... 

The total capacity of a ruthenium oxide electrode [the usual double-layer capacity plus the pseudocapacity of reaction (21.4)] is rather high (i.e., several hundred F/g), even more than at the electrodes of carbon double-layer capacitors. The maximum working voltage of ruthenium oxide pseudocapacitors is about 1.4 V. 

Lee HY, Kim SW, Lee FTY. Expansion of active site area and improvement of kinetic reversibility in electrochemical pseudocapacitor electrode. Electrochemical and solid state letters 2001 4(3) A19-A22. 

ECs are another promising electrical energy storage device with a higher energy density than electrical capacitors, and a better rate capability and cycling stability than LIBs [32]. Carbon-based electric double layer capacitors and metal oxide- or polymer-based pseudocapacitors are two main types of ECs. The charge-... 

Recently supercapacitors are attracting much attention as new power sources complementary to secondary batteries. The term supercapacitors is used for both electrochemical double-layer capacitors (EDLCs) and pseudocapacitors. The EDLCs are based on the double-layer capacitance at carbon electrodes of high specific areas, while the pseudocapacitors are based on the pseudocapacitance of the films of redox oxides (Ru02, Ir02, etc.) or redox polymers (polypyrrole, polythiophene, etc.). 

In the second type of supercapacitor, sometimes termed pseudocapacitors, redox capacitors or electrochemical capacitors, the non-Faradaic doublelayer charging process is accompanied by charge transfer. This Faradaic process must be characterized by extremely fast kinetics in order to allow device operation with high current density discharge pulses. 

Depending on the charge storage mechanism, one must distinguish between the electrical doublelayer capacitors (EDLC) and the pseudocapacitors. The principles and properties of both types of supercapacitors will be further described. 

Capacity also influences the energy value. Actually, most of the research effort is dedicated to improving the capacity of electrode materials. Since ACs are taken as reference, the cost of the materials is an important criterion at the industrial level. Most of the materials developed for EDLC are of little interest for applications, because of their cost and only slightly improved performance. By contrast, it will be shown that advanced carbon materials can be developed for pseudocapacitors. 

In general, two modes of energy storage are combined in electrochemical capacitors (1) the electrostatic attraction between the surface charges and the ions of opposite charge (EDL) and (2) a pseudocapacitive contribution which is related with quick faradic charge transfer reactions between the electrolyte and the electrode [7,8], Whereas the redox process occurs at almost constant potential in an accumulator, the electrode potential varies proportionally to the charge utilized dr/ in a pseudocapacitor, which can be summarized by Equation 8.5 ... 

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