Double-layer supercapacitors

Qu D., Studies of the activated carbons used in double-layer supercapacitors, J. Power Sourc. 2002 109 403-411. 

Fig. 9.27 shows the variation of capacitance as a function of the surface area from which it may be concluded that in principle it is possible to obtain double-layer supercapacitors having specific capacitance of the order of 100 F/g so that values of practical capacitance density as high as 30 F/g can be predicted. 

A typical configuration of a double-layer supercapacitor involves two metallic collectors which hold in place the carbon powder electrodes, which in turn are separated by an electrolyte, in most of the cases formed by liquid solutions (Fig. 9.28.) A layer of porous, non-conductive material acts as a separator. 

Fig. 9.27 Specific capacitance of a double-layer supercapacitor as a function of surface area. (By permission of Chim Ind . E. Spila et al., 1995, 77, 333.)...

Solid ionic conductors can also be used in the fabrication of solid state double-layer supercapacitors. An example is the device developed in the late 1960s by Gould Ionics which adopted a cell system using a silver-carbon electrode couple separated by the highly ionically conducting solid electrolyte RbAg4I5 (see Section 9.1) ... 

Verbrugge M, Liu P. Microstructural analysis and mathematical modeling of electric double-layer supercapacitors. Journal of the Electrochemical Society 2005 152(5) D79-D87. 

Belhachemi F, Rael S, Davat B. A physical based model of power electric double-layer supercapacitors, IEEE-IAS 00, Rome, 2000. 

Capacitors can be polarized or non-polarized, depending on the - dielectric. Non-polarized devices have dielectrics consisting of ceramics or polymers (such as polystyrene, polyester, or polypropylene). They are normally box-shaped and their capacity is usually in the range from pF to pF, the maximum voltage up to 1000 V. Polarized capacitors are electrochemical devices the dielectric is an anodic oxide of A1 (pF to 100 mF, potentials up to 1000 V), Ta (capacities pF to 100 pF, potentials up to 20 V), or Nb (- electrolytic capacitor) or a double layer (- supercapacitor, capacities up to some 10 F and potentials up to 2.5 V or 5 V). Aluminum electrolytic capacitors are normally of cylindrical shape with radial or axial leads. Tantalum capacitors are of spherical shape and super capacitors form flat cylinders. 

As follows from these tables, symmetrical double-layer supercapacitors based on C/C-type carbon electrodes and, in limited quantities, some hybrid C/NiOOH-type ECSCs are produced at present. In the case of pseudocapacitors based on electron-conducting polymers, there are as yet only laboratory prototypes. 

Niu, J., W. G. Pelf and B. E. Conway. 2006. Requirements for performance characterization of C double-layer supercapacitors Applications to a high specific-area C-cloth material. Journal of Power Sources 156 725-740. 

FIG U RE 2.3 Ragone plots for the fully charged carbon-cloth electrode for various constant currents as marked on the figure for four electrolyte eoncentrations 0.01 M ( ), 0.05 M ( ), 0.5 M (A), and 5 M (t). (Reprinted from Journal of Power Sources, 156, Niu, J., W. G. Pell, and B. E. Conway, Requirements for performance characterization of C double-layer supercapacitors Applications to a high specific-area C-cloth material, 725-740, Copyright 2006, with permission from Elsevier.)... 

Skinner B, Chen T, Loth MS, Shklovskii BI (2011) Theory of volumetric capacitance of an electric double-layer supercapacitor. Phys Rev E 83 056102... 

Figure 4.16 Structure of a double-layer supercapacitor (reprinted with permission from [121]).

Gouerec P, Miousse D, Tran-Van F, Dao LH (1999) Characterization of pyrolyzed polyacrylonitrile aerogel thin films used in double-layer supercapacitors. J New Mater Electrochem Syst 2 221-226 Woignier T, Reynes J, Phahppou J, Dussossoy JL, Jacquet-Francillon N (1998) Sintered sUica aerogel a host matrix for long life nuclear wastes. J Non-Cryst Solids 225 353-357... 

This chapter will provide a comprehensive discussion of the fundamentals of double-layer supercapacitors, including the electric double-layer charging and discharging mechanism, the theoretical principles that govern their operation, and their structural designs. 

See color insert.) Electric double-layer supercapacitor. 

Commercially available carbon particles such as active carbon powders are the most common active electrode materials for double-layer supercapacitors. They can have surface areas between 1000 and 3000 m. g i. When this kind of carbon material is used to make the electrode layers and no electrochemical reaction is employed for charge generation, the resulting devices are called double-layer supercapacitors. 

Figure 2.12 shows an electrode layer in a double-layer supercapacitor. This electrode layer is composed of carbon particles and a binder. In the layer, the sources of the capacitance are the pores on the carbon particles and the porous channels within the matrix layer. It is obvious that only locations that are accessible by the electrolyte ions can form the electrode-electrolyte double-layer for capacitance generation. 

Electrochemical Double-Layer Supercapacitors 2.5.1 Structure and Capacitance... 

The structure of an electrochemical double-layer supercapacitor is similar to that of a battery two electrodes comprised of a carbon material as shown... 

For electrochemical double-layer supercapacitors, the two electrodes are identical, meaning that Therefore, Equation (2.33) can be con-... 

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