Supercapacitor Basics (EDLCs, Pseudo, and Hybrid)

Over the past few years, supercapacitors have been spotlighted because of the challenges faced by other energy storage systems. The supercapacitor possesses excellent power density and long-term durability with an eco-friendly nature. Due to their wide range of advantages, supercapacitors are applicable especially in electric vehicles, heavy-duty vehicles, telecommunication, electric aircraft, and consumer electronic products. As per the charge storage mechanism, supercapacitors are divided into three categories based on their charge-storing method: electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid capacitors. The electrode materials such as graphene, activated carbon, metal oxides, conducting polymers, etc., were widely applied, for better performance. The electrolyte is a crucial component in the mechanism of the supercapacitor to run the system at a higher voltage and thus there are various electrolytes such as solid, inorganic, and organic based on the application of the materials, and the electrolytes are chosen. However, the supercapacitors suffer from low energy density. Currently, research is more focused on advanced materials and various synthesis methods to overcome the drawbacks. This chapter provides a detailed understanding of supercapacitors with redox and non-redox reactions -the broad classification of the supercapacitor -their charge storage mechanism -various electrode materials -electrolytes (aqueous, non-aqueous, and solid) and current collectors, etc. Finally, the parameters that help in estimating the performance of supercapacitors are (specific capacitance, energy density, and power density) included.