In recent years, many reviews about single conventional capacitors, single supercapacitors, and single metal ion HCs have been widely reported. However, the comprehensive review for conventional capacitors, supercapacitors, and emerging hybrid ion capacitors has received little concern.
Regarding the supercapacitors, the carbon materials with high specific surface area were bearing the brunt. Then, the appearance of conduct polymers and transition metal oxides was employed to enlarge specific capacitance and specific energy.
On the contrary, the common terminology cathode and anode do not seem appropriate for electrochemical capacitors. It's due to the fact that energy delivery process may not require redox reactions . Other terms for ECs are super capacitors or ultra-capacitors or hybrid capacitors.
The types of SCs are gathering momentum due to their high specific P d, high C s, zero maintenance requirements, high E d, absence of memory effect and possibility to cross distance among the capacitors, which practically escalates the performance .
Moreover, recent advancements in energy storage technology have led to significant improvements in the performance of ED capacitors. New materials such as graphene and carbon nanotubes have increased energy density, while hybrid capacitors combining ED with pseudocapacitive materials have enhanced power density.
The conventional capacitors, as a passive electronic component, are composed of two adjacent conductors and an insulating medium between them. In 1745, the invention of the Leyden jar opened the door of capacitor technology. [ 21 ] Thereafter, a series of representative capacitors came out one after another.