Abstract
In this chapter, the types of electrolytes and the alteration in capacitance
with pore size, their power density, and energy density along with the interaction of
electrolytes with current collectors are discussed. The electrolytes’ electrochemical
stability broadly estimates the working cell voltage provided that the electrodes are
stable under operating cell voltage. The electrolytes are divided into various categories
such as liquid electrolyte, solid-state, and redox-active electrolyte. The liquid
electrolytes are further categorized into aqueous and non-aqueous electrolytes. The
critical performance parameters such as stability, lifetime, operating temperature,
operating voltage, etc. are believed to be affected by electrolytes. Moreover, the
electrolytes are believed to interact with the current collectors, additives, binders,
separators, and electrode material to affect the practical performance of
supercapacitors. However, the capacitance of the electrolyte depends upon the ion size
and the matching between the electrode pore size and electrolyte ion size. The power
density and energy density depend upon the potential window, ionic conductivity, and
electrochemical stability along with concentration, respectively. Further, the ionelectrode interaction is supposed to affect the cycle life and power density as well. The
thermal stability of electrolytes depends upon their boiling points, freezing points, and
salt solubility and the equivalent series resistance depends upon ion conductivity,
mobility, and viscosity.