Supercapacitors are electrochemical energy storage devices. The structure of a
supercapacitor is similar to that of a battery. It consists of two porous electrodes with a
current collector on each electrode immersed in an electrolyte separated by a dielectric
porous separator. When a voltage potential is applied across the current collectors, the
positive electrode attracts negative ions in the electrolyte, while the potential on the
negative electrode attracts positive ions. The charge accumulated at both electrode
surfaces generates energy when discharging (Figure 2.1). The components made up of
the supercapacitor including the electrodes, the separator, the current collector, as well
as the electrolyte all are important factors affecting the overall performance of the
device that must be considered in designing a high-performance supercapacitor device.