Basic concepts of supercapacitors

This chapter aims to provide a general description on the fundamental aspects regarding supercapacitors (capacitors), which are important when developing new nanomaterials for such applications. An electric capacitor usually consists of two conductive plates, known as electrode and made of metals, between which a piece of dielectric material is inserted as shown in Fig. 2.1 [1]. Dielectrics that can used to construct a capacitor include air (vacuum), oiled paper, mica, glass, porcelain and various titanates. As an external voltage is applied across the two electrodes, the charging process occurs, during which, positive charges are accumulated on the positive electrode, whereas negative charges are accumulated on the negative electrode. After the external voltage is removed, both the positive and negative charges are still at the electrodes. Therefore, the capacitor separates the electrical charges. Once the two electrodes are connected with a conductive wire, the discharging process takes place, during which the positive and negative charges will be combined through the conductive wire. As a result, the capacitor can be used to store and deliver the charges.