A comprehensive review on fundamentals and components of zinc-ion hybrid supercapacitors

With the surge in demand for energy storage devices, better and safer alternatives are required. Zinc ion hybrid supercapacitor (ZHSC) has a great potential as an alternative to lithium-ion batteries as it combines the high energy capacity of zinc-ion batteries and longevity and high power density of supercapacitors to produce a device that can potentially outperform and outlast conventional batteries. ZHSCs are currently unable to achieve their theoretical specific capacity due to several issues that are stated in the review. This review aims to provide fundamentals of the energy storage mechanism of hybrid supercapacitors and ZHSCs as well as summarize recent developments on ZHSCs. Various types of carbon-based materials along with pseudocapacitive materials that have been utilised as electrode materials for ZHSCs are comprehensively discussed. The zinc anode as well as ways to improve its performance are briefly discussed in the review. Electrolyte for ZHSCs with a focus on hydrogel polymer electrolyte and how it affects ZHSC performance is elaborated. Lastly, a summary of current issues faced by ZHSCs, and future perspectives are discussed.