Surfactant-Dependent Flower and Grass Like Zn0.76Co0.24S/Co3S4 for High-Performance All-Solid-State Asymmetric Supercapacitors

A simple method for establishing a class of electrode materials with excellent electrochemical performance for use as supercapacitors is urgently needed. Composite electrode materials, Zn0.76Co0.24S/Co3S4, with different morphologies on three-dimensional nickel foam have been fabricated for the first time using a facile hydrothermal method and successive anion exchange technique. Different surfactants, ammonium fluoride (NH4F) or polyvinylpyrrolidone (PVP), contributed to developing various morphologies, with hexamethylenetetramine (HMT) serving as the alkaline source. The mechanisms of the surfactants that acted on the morphologies of the electrode materials were analyzed by adjusting their ratios. The NH4F actuated flower-like Zn0.76Co0.24S/Co3S4 demonstrated a superior specific capacitance of 2798.16 F g−1 at 5 mA cm−2 and retained outstanding cyclic stability of 93.8% after 7000 cycles, compared to the grass-like Zn0.76Co0.24S/Co3S4 actuated by PVP. The assembly of the all-solid-state asymmetric supercapacitor (ASC), flower-like Zn0.76Co0.24S/Co3S4//RGO, resulted in a high energy density of about 62.22 W h kg−1 and a maximum power density of 16 kW kg−1, as well as a long cycle life (86.3% of capacity retention after 8000 cycles). This comprehensive study on the control of the morphologies of transition metal sulfide composites by surfactants provides a general method to synthesize multicomponent electrode materials for energy storage devices.