In situ growth of nickel cobalt sulfide on carbon cloth by electrodeposition as binder-free electrode for supercapacitor

Abstract

Development of binder-free electrode of pseudocapacitive material with excellent cycling stability for supercapacitor shows great attraction in energy storage market. Here, nickel cobalt sulfide (NCS) has been successfully grown on carbon cloth (CC) by electrodeposition in a sulfate-based electrolyte solution with thiourea (TU) as sulfur source and chelation agent. The results show that the chemical composition, microstructure and electrochemical performance of the as-prepared electrode can be modulated by tunning the deposition overpotential. The oriented growth of NCS nanosheets driven by electric field coupled with thiourea adsorption endows the deposits with intersected porous nanosheet-array microstructures, which enables the fast electronic and ionic transmissions. The optimal electrode prepared under −1.0 V (vs Ag/AgCl) (denoted as NC2S200–1.0/CC) can deliver a discharge specific capacitance of 909.5 F g⁻¹ at 1 A g⁻¹, which can maintain 89.2 % at 10 A g⁻¹, demonstrating outstanding rate performance. As successively charging and discharging for 4000 cycles at 5 A g⁻¹, 120.6 % of the initial value can be retained, illustrating exceptional cyclic stability. In addition, the assembled NC2S200–1.0/CC//AC asymmetric supercapacitor can exhibit an energy density of 26.2 Wh kg⁻¹ which corresponds to a power density of 821.1 W kg⁻¹, when charging-discharging at 2 A g⁻¹ for 10000 cycles, a capacitance retention of 75.5 % can be achieved, manifesting good cycling stability. This work provides a new idea for fabricating transition metal sulfides supported binder-free electrode by electrodeposition.