Fundamentals of Electric Capacitors

By using porous carbon materials with a veiy high surface area in both positive and negative electrodes, a large amount of electrical charge was found to be stored, and electric double-layer capacitors (EDLCs) were developed [81,82], The fundamental concept of this capacitor is the formation of electric double-layers on the surface of electrodes, as illustrated in Fig. 28. The total amount of electeic charges aligned in double layers on both electrodes increases by the application of potential difference and it is easily understood to depend on the area of this interface, i.e. the surface area of solid electrodes. 

This chapter describes the fundamentals of different kinds of electrochemical capacitors (ESs), including electrical double-layer capacitors (EDLCs), pseudocapacitors, and hybrid ESs. This serves as a foundation for understanding ES science... 

Electrostatics provides the archetype of poles and dipoles, which are very old concepts. They have been The electric capacitor is a used as templates for the fundamental capacitive dipole generalization made in the storing capacitive... 

Reed CW, Cichanowski SW (1994) The fundamentals of aging in HV polymer-fihn capacitors. IEEE Trans Dielectr Electr hisul 1 904... 

While introducing this new way of obtaining electroanalytical data, we will need to rely on the analogies between an electrochemical cell (or sample) and an electrical circuit made up of resistors and capacitors assembled in order to mimic the current-voltage behaviour of the cell. All the time, though, we need to bear in mind that the ideas and attendant mathematics are for interpretation only, although they are fundamentally very simple. 

The electrochemical impedance is a fundamental characteristic of the electrochemical system it describes. A knowledge of the frequency dependence of impedance for a corroding system enables a determination of an appropriate equivalent electrical circuit describing that system. Such a circuit is typically constructed from resistors and capacitors. Table 1 shows the transfer functions... 

In the liquid phase the topics of principal concern are adsorption and proton and/or electron transfer across the electric donble layer. Carbon materials are unique in these applications becanse they are insolnble over the entire practical range of pH, are amphoteric, and can exhibit either acidic or basic properties this was illustrated in Fignre 1.10. Furthermore, because of their more or less extensive delocalized k-electron system in the graphene layer, they can either accept or donate electrons. Snch remarkable flexibility offers, on the one hand, a nniqne opportnnity to tailor carbon s properties to specific needs in adsorption, catalysis, and electrocatalysis but, as argued in detail elsewhere [24], it is also responsible for the persistent lack of fundamental nnderstanding in the increasingly important field of carbon electrochemistry, despite the tremendous amount of research and development focused on carbon-based capacitors, batteries, and fnel cells. 

Fig, 28. Fundamental concept for the electric double-layer capacitor. Courtesy of Dr. A. Nishino. 

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