ABSTRACT
Over the past decades, among various electrochemical energy storage devices, supercapacitors, also called ultracapacitors, have drawn immense curiosity as a special class of energy storage devices in both academia and industry due to their distinct advantages such as higher power density, fast charging-discharging rate (in seconds), excellent stability, and a long cycle life (>100,000 cycles) in comparison to conventional capacitors, batteries, and fuel cells. However, the type of electrolyte is a significant component in governing the overall performance of electrochemical supercapacitors (ESs). Hence, it is mandatory to enhance the energy characteristics such as energy density and cycle life of the supercapacitors, which depend on the type of electrolytes used. Most commercially available ESs use organic electrolytes due to their wide operating voltage. Aqueous electrolytes have been broadly used in research and development because of their easy handing in the laboratory in contrast to organic electrolytes and ionic liquids, which are expensive, flammable, and in a few cases, toxic, as well as require hard purification measures under a rigorously controlled atmosphere to avoid preface of moisture. This chapter embraces the latest accomplishments in this area and affords an insight into the development of aqueous electrolytes.
