Copper tungsten sulfide anchored on Ni-foam as a high-performance binder free negative electrode for asymmetric supercapacitor

Transition binary metal sulfides have fascinated much attention as electrode materials for energy storage applications. Herein, we report the use of binder-free copper tungsten sulfide (CWS) anchored on Ni foam and investigated its electrochemical properties as a negative electrode for supercapacitor application. The mechanism of CWS growth on the surface of Ni foam via hydrothermal process is explained based on recrystallization of metastable precursors (RMP) process and confirmed using laser Raman spectroscopic analysis. The electrochemical analysis using three-electrode configuration reveals that the charge-storage mechanism is due to the Type-B pseudocapacitance (due to intercalation with partial redox) nature of the CWS/Ni electrode with a high specific capacitance (areal capacitance/specific capacity) of 2666.6 F g(-1) (888.8 mAh g(-1)/1866.6 mF cm(-2)) at a constant current of 10 mA. To emphasize the potential use of CWS/Ni electrode in energy storage sector, we fabricated an asymmetric supercapacitor device using CWS/Ni (negative electrode) and graphene (positive electrode) which delivers a device specific capacitance (107.93 F g(-1)/226.67 mF cm(-2)) with a high energy density (48.57 Wh kg(-1)/102 mu Wh cm(-2)), and excellent electrochemical stability for 10,000 charge-discharge cycles. These results confirm that the CWS/Ni electrode can act as an effective energy-storage electrode material for high performance supercapacitors.