Recent progress in copper sulfide based nanomaterials for high energy supercapacitor applications

Copper sulfides (CuxS, x = 1?2), have been recognized as industrially significant materials with diverse applications in exotic technological fields of electronics, sensors, catalysis, photovoltaics, energy storage, etc. Their promising electrochemical performance, ease of availability, and low production cost have motivated enormous interest in fabricating high-performance supercapacitors to meet the sky-rising demands for proficient electrochemical energy storage devices. Various copper sulfide nanostructures obtained via different synthetic methodologies to design superior electrode materials for high-energy supercapacitors have been briefly outlined here. The variations in capacitive behavior with diverse copper sulfides morphologies have been compared and elaborated. As pristine metal chalcogenides nanomaterials often suffer a high rate of agglomeration, irreversible volume change during large electrochemical cycles in addition to poor charge transport features, their commercial usage gets severely restricted. Accordingly, to overcome the aforesaid limitations and bring about superior material qualities, copper sulfides have been intimately blended with a range of other electro-active materials like inorganic semiconductors including metal oxides, hydroxides, chalcogenides, carbides, etc., conducting polymers including polyaniline, polypyrrole, derived polythiophenes, etc. as well as with diverse carbon-based systems in the form of activated carbons, carbon nanotubes and functionalized graphene systems, etc., to furnish varieties of exquisite binary, ternary and quaternary nanocomposites. These materials have exhibited improved features, especially, in terms of capacitance, energy, and power efficiencies besides offering good mechanical flexibility and environmental stability to be applied in various energy-seeking fields of global technology. To the best of knowledge, very few review reports are available in the literature that highlights systematic as well as comprehensive discussion on the extent of progress of supercapacitive applications of different copper sulfide nano-systems and their nanocomposites. Besides, this study also outlines the current challenges faced as well as figures out some prospective ways that may promote better strategic sketching of smarter copper sulfides-based nanomaterials for high-performing supercapacitors in the upcoming days.