Rapid Synthesis of Hierarchical Cobalt Disulfide Nanostructures by Microwave-Assisted Hydrothermal Method for High Performance Supercapatteries

The energy crisis is a widely discussed topic due to the rapid unprecedented increase in the population. The only solution to this issue is to couple sustainable and renewable energy conversion technologies with electrochemical energy storage devices. Supercapacitors and rechargeable batteries are the two choices for energy storage systems. Supercapacitors deliver high power but fail in providing high energy density. On the other hand, rechargeable batteries are excellent in their energy density but possess low power density. Hence, energy scientists and material researchers put their research focus on developing electrochemical energy storage devices that exhibit both high power and energy densities. This has reached the invention of an energy storage device, named the supercapattery, having both the features of batteries and supercapacitors. The electrodes in supercapatteries possess both surface-controlled (supercapacitive) and diffusion-controlled (battery-type) charge storage mechanisms. Transition metal sulfides are potential candidates with excellent electrochemical performance. Herein, we report the facile synthesis of cobalt disulfide (CoS2) nanostructures via a microwave-assisted hydrothermal method with a short processing time. The CoS2 nanostructures are obtained by varying the composition of the transition metal to sulfur ratio by controlling the precursor concentrations. An asymmetric supercapattery cell tested with CoS2 as positrode and activated carbon as negatrode exhibits a mass specific capacity of 120.58 C/g at a current density of 1.2 A/g. The electrode-active material has higher electrochemical thermal stability and cyclic stability, which indicates its efficiency for commercial applications.