Progressive updates on nickel hydroxide and its nanocomposite for electrochemical electrode material in asymmetric supercapacitor device

Transition metal oxides/hydroxides have received a lot of attention due to their perfect capacitive performance, low cost, and environmentally benign nature in supercapacitor applications. Among them, nickel hydroxide (Ni(OH)2) has been widely selected for studies because of its stimulating feature of ultrahigh theoretical capacitance. However, the low conductivity and inadequate rate capability impede its wide-scale use which is overcome by incorporating Ni(OH)2 with polymers, metal oxides, and carbonaceous substances to create binary nanocomposite materials. However, there are some issues that hinder its commercialization and the state of progress is still far from being feasible. Hence, it is observed from the literature that the integration of the above mentioned three components by properly optimizing the percentage of each component in the composite such as mass loading and selection of an appropriate electrolyte leads to enhanced electrochemical performance. Further, it is observed that asymmetric supercapacitors perform better than symmetric ones because employability of two different electrode materials widened the potential window which also provides a workaround for the symmetric supercapacitor's energy storage constraints. In the present review, progressive updates on Ni(OH)2 based materials are explored which includes a brief on synthesis, material characteristics, and supercapacitor outcomes. Further, critical issues and potential solutions along with suggestions have also been discussed for how this set of resources might develop in the future for asymmetric supercapacitor devices.