Electrochemical capacitors types

EFFECT OF CARBONACEOUS MATERIALS ON PERFORMANCE OF CARBON-CARBON AND CARBON-Ni OXIDE TYPES OF ELECTROCHEMICAL CAPACITORS WITH ALKALINE ELECTROLYTE... 

Testing in the Carbon-Carbon type of Electrochemical Capacitors... 

For electrochemical capacitors of the system carbon-carbon, in spite of the fact that the electrode body consists of conductive activated carbon, it is always necessary to use highly conducive additives, preferably those selected from the group of carbon materials. Exact type of additives plays a secondary role for this type of an EC, as it operates in the so-called safe voltage interval (l,12-l,24v), where limited to no oxidation of carbon takes place in this range of voltage. 

As it logically follows from the considered mechanism and the existing experimental data, PANI-type conductive polymers can certainly be used to improve the characteristics of electrochemical capacitors. According to our estimations, a specific capacity of electrodes with conductive polymers could be increased by as much as to 3-5 times over that of the classical carbon electrodes. 

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. 

Fig. 9.30 Constant current (200 mA) discharge curves for the three types of polymer electrochemical capacitor...

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],... 

Recent application of conducting polymers for electrochemical capacitors has been reviewed. The ionically conducting polymers have the potential to replace wet-type capacitors by dry-type ones. Especially important are the gel electrolyte systems whose ionic conductivity is high, and thus high capacitance can be obtained with them in EDLC. We believe that the combination of high surface area... 

Three types of electrochemical capacitors (I, II, and HI) are known with ECPs as active electrode materials. Type I corresponds to a capacitor based on a symmetrical configuration with identical active materials based on p-doped ECPs (e.g., based on PPy) on both electrodes. Eigure 28.5 shows charging-discharge chrono-voltammograms characterizing the behavior of ECSCs with two PPy-based electrodes (Volfkovich and Sedyuk, 2002). As we see, they have the shape of straight lines for conventional capacitors. 

Conway, B. E., and W. G. Pell. 2003. Double-layer and pseudocapacitance types of electrochemical capacitors and their applications to the development of hybrid devices. Journal of Solid State Electrochemistry 7 637-644. 

Lota, G., M. Walkowiak, G. Schroeder, and B. Gierczyk. 2013. Electrochemical behavior of tripodand-type silanes as electrolyte solvents for electrochemical capacitors. International Journal of Electrochemical Science 8 9222-9230. 

Gottesfeld and co-workers at Los Alamos National Laboratory proposed in 1994 a classification of conducting polymer-based electrochemical capacitors as schematically presented in Figure 15.6 [11], The first one is a symmetrical capacitor which involves the same p-dopable polymer for both electrodes and was called the Type I capacitor. Polypyrrole [11, 37, 47] and polyaniline [48] were commonly used as active electrode materials for the Type I capacitor. When the Type I capacitor is fully discharged, both electrodes are in a half-doped state. 

Figure 15.6 Schematic representation of the three types of electrochemical capacitor that can be assembled with p- and n-dopable conducting polymers. The cell voltage that could be expected from these capacitors is given on the left-hand side of each capacitor type...

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