Hydrothermal synthesis of Zn-doped CuS as a binder-free positive electrode material for supercapacitor applications

Transition metal sulphides have received much attention due to their high theoretical specific capacity and good electrochemical stability. Among them, CuS has emerged as a favorable option owing to its affordability, diverse nanostructures, and metallic electronic conductance. However, despite its good initial capacitance performance, copper sulfide exhibits poor performance in terms of long-term stability. The doping of Zn can alter the crystal structure of copper sulfide, thereby enhancing its stability in electrochemical applications and improving the cycling stability of the supercapacitor. In this study, zinc-doped CuS materials were synthesized via a hydrothermal method and utilized as the positive electrode material for supercapacitors. Notably, in a three-electrode system, at a current density of 4 mA cm−2, the specific capacitance of the electrode material can reach 3980 mF cm−2. Moreover, at a current density of 20 mA cm−2, the capacitance retention rate reaches 85% after 5000 cycles. Furthermore, the assembled hybrid supercapacitor (Zn–CuS//activated carbon) maintains a capacitance retention rate of 78% after 4000 cycles at a current density of 20 mA cm−2. The excellent electrochemical performance observed in this study provides valuable insights for the design of high-performance electrode materials for supercapacitors.