10. Characteristics of Electrolytes

Electrolytes play a major role in determining the energy-storage capacity of the electrochemical supercapacitor devices. It consists of solvent, dissociated positive and negative ions, or pure salt, i.e., a solvent-free ionic liquid. The properties of an electrolyte depend on a number of parameters such as size of the ion and concentration, conductivity, interaction between electrolyte, electrode materials, etc. In this chapter, the types of electrolytes used in electrochemical supercapacitors have been discussed in detail. Based on chemical nature, the electrolytes can be classified in various groups, i.e., aqueous, organic, ionic liquid, solid state, redox, etc. This chapter also points out the effect of these electrolytes on the cell voltage, specific capacitance, and other important parameters for electrochemical double layer, asymmetric, and hybrid supercapacitor devices.