ABSTRACT
The electrolyte is one of the central components of electrochemical supercapacitors (ESs) and consists of a solute dissolved in the solvent or pure salt (in the case of solvent-free ionic liquids [ILs]). The electrolyte plays an important role in the ES in several ways such as: (1) providing ionic conductivity and thus allowing for charge compensation on each electrode in the ES cell; (2) contributing to the formation of an electrical double-layer (EDL) in electrical double-layer capacitors (EDLCs); and (3) participating in the charge storage processes (reversible redox reactions) in pseudocapacitors. As a result, the electrolyte can greatly inuence the performance of ESs, as shown in Figure 1.2. In addition, Table 2.1 lists some commercialized ESs and their corresponding performance properties [1]. The majority of these ESs use organic electrolytes with a cell voltage of 2.5-2.8 V (only three of them can achieve 3.3 and 3.8 V cell voltage). Most ESs with organic electrolytes use the acetonitrile (ACN) solvent while others apply the propylene carbonate (PC) solvent.
