Design and fabrication of MOF-derived leaf-like Zn-Co-S nanosheet arrays decorated with Ni-Zn-P ultrathin nanostructure for hybrid supercapacitors

Abstract

Transitional Metal phosphides and sulfides are considered a promising electrode material in energy storage sources due to their high electronic conductivity, rich valences and high electrochemical activity, and excellent stability. Here, we report porous Ni-Zn-P/Zn-Co-S hybrid nanostructures on nickel foam as a novel free-binder electrode achieved via a facile three-step immersion procedure, a sulfurization process, followed by an electrodeposition approach consisting of leaf-like Zn-Co-S nanosheet arrays covered with ultrathin Ni-Zn-P nanosheets. The unique multicomponent heterostructure of Ni-Zn-P/Zn-Co-S can possess the large accessible surface area, more active sites, promotes free diffusion of electrolytes, shortens the path of electron transfer in electrochemical reaction process, and the synergistic effect from both components, leading to better electrochemical performances. The Ni-Zn-P/Zn-Co-S electrode demonstrates outstanding electrochemical performance, including ultrahigh specific capacitance of 2803 F g−1 at 1.0 A g−1, favourable rate capability, and supreme stability with 91.3% capacitance retention after 3000 cycles.More importantly, a prototype hybrid asymmetric supercapacitor is assembled based on Ni-Zn-P/Zn-Co-S as the battery-type electrode and rGO as the capacitive-type electrode. The fabricated device has a capacitance of 94.51 F g−1 at 2.3 A g−1 and demonstrates an energy density of 30.6 Wh kg−1 at a power density of 1742 W kg−1 with a remarkably long cycle life. This work delivers a simple and innovative strategy to develop advanced binder-free electrodes as a next-generation energy storage system.