Zinc cobalt sulfide nanosheets grown on nitrogen-doped graphene/carbon nanotube film as a high-performance electrode for supercapacitors

Abstract

To improve the energy density of supercapacitors, a new type of electrode material with high electrochemical activity and favorable morphology is extremely desired. Ternary metal sulfides with higher electrochemical capacity and activity than mono-metal sulfides hold great promise in the field of energy storage devices. Herein, an advanced electrode composed of zinc cobalt sulfide nanosheets supported on sandwich-like nitrogen-doped graphene/carbon nanotubes (NGN/CNTs) film has been successfully fabricated through a two-step synthesis. Benefiting from the characteristic features and 3D electrode architectures, the Zn_0.76Co_0.24S electrode exhibits a high specific capacitance of 2484 F g⁻¹ at 2 A g⁻¹ and excellent cycling stability (almost no capacitance fading after 10 000 cycles at 30 A g⁻¹). This creative nanostructure design of ternary transition metal sulfides could provide a promising prospect for application in energy storage devices. Moreover, an asymmetric supercapacitor was also fabricated by using Zn_0.76Co_0.24S/NGN/CNTs film as the positive electrode and NGN/CNTs film as the negative electrode, exhibiting a high energy density of 50.2 W h kg⁻¹ at 387.5 W kg⁻¹ and superior cycling stability of 100% initial capacity retention over 2000 cycles. This creative nanostructure design could provide a promising new way to develop high-performance supercapacitors and shed new light on configuring carbon-based ternary transition metal sulfide electrode materials in energy storage and conversion devices.