Microflower CuS:Ni as a negative electrode with battery-type behavior for all transition-metal-sufides-based high-performance asymmetric supercapacitors

Extensive research on high-energy-density supercapacitors has pushed the development of asymmetric supercapacitor (ASC) to achieve a high-energy-density supercapacitor. Transition metal sulfides have been identified as highly promising pseudocapacitor materials, thanks to their design playing which significantly influences their performance. A simple and fast synthesis protocol, namely hot-injection method, was used to produce both positive and negative electrodes, which were then assembled as asymmetric supercapacitors. The negative electrode of copper sulfide (CuS) was doped with Nickel (Ni) to enhance its performance. The role of Ni dopant role in enriching the redox reactions was fully analyzed through both of electrochemical characterization and density functional theory (DFT) calculation. A 20n% Ni-doped CuS (CuS:Ni) negative electrode was successfully synthesized which showed a high specific capacity of 714 C/g at 1 A/g. Combined with NiS, an asymmetric supercapacitor was assembled, which exhibit a high specific capacity of 435 C/g (at 1 A/g) and a high energy density of 61.87 Wh/kg (at 517.86 W/kg). A new generation of asymmetric supercapacitor with outstanding performance can be made with all transition metal sulfide.