Super capacitors for energy storage: Progress, applications and challenges

Nowadays, the energy storage systems based on lithium-ion batteries, fuel cells (FCs) and super capacitors (SCs) are playing a key role in several applications such as power generation, electric vehicles, computers, house-hold, wireless charging and industrial drives systems. Moreover, lithium-ion batteries and FCs are superior in terms of high energy density (ED) as compared to the SCs. But, the down-side associated with them is the low power density (PD). On the other hand, this high PD feature is essential for the enhancement of dynamic performance of the system. Therefore, the SCs are well utilized due to their dominant features such as high specific power, rapid charging-discharging rate and superior cycling life. Hence, this paper mainly focuses on the advancements of various types of SCs along with their performance improvement methods. The important properties and selection of the electrode and electrolyte materials are described in detail. The commercially available SCs are enumerated with much more emphasis on their Figure of Merits (FOMs). Furthermore, the prominent role of SCs is highlighted with respect to the aforementioned applications. Finally, the future challenges associated with the SCs are presented. This review paper gives insightness for the design engineers and researchers in order to fill the research gaps associated with the SCs.