ABSTRACT
This chapter provides 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. The electric double-layer theory is the foundation of electrochemistry from which the electrochemical processes occurring at an electrostatic interface between a charged electrode material and an electrolyte are investigated. The most popular electrode materials used to construct electrochemical supercapacitors are carbon-based nanoparticles and related composite materials that have high surface areas, giving high capacitances. In supercapacitors, the electrolyte concentration is normally high, causing the diffuse layer to disappear and the Helmholtz layer to remain. This increases the capacitance of the electrode layer and allows more charge storage. Energy density is one of the most important parameters for evaluating an electrochemical supercapacitor. To generate more energy and power, a number of single supercapacitors can be stacked together and several such stacks can be connected to form an energy bank.
