关键词: 钴酸锌, 氟化铵, 面积比容量, 非对称超级电容器

Abstract: In this work, hydrothermal reaction and high temperature were used to grow ZnCo₂O₄ active materials on Ni foam. The crystal stuctures and surface morphlogies of four samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The electrochemical performances were characterized by cyclic voltammetry (CV)、galvanostatic charge/discharge (GCD) testing and electrochemical impedance spectroscopy (EIS) on an electrochemical station. It can be seen that active materials tended to form denser stuctures with an increasing amount of NH₄F in the solution system and four different morphologies of ZnCo₂O₄  were obtained: nanoneedles, thin nanoneedles-clusters, thick nanoneedles-clusters, and lozenge-like bulks.ZnCo₂O₄ with the thin nanoneedles-clusters morphology held the best electrochemaical performance with the capacitance of 2.77 F·cm^-2 at the current density of 5 mA·cm^-2. A button asymmetric supercapacitor (ZnCo₂O₄ -2/NF//AC/NF) assembled with ZnCo₂O₄ -2/NF and AC/NF exhibited the excellent performance in energy storage. The button asymmetric supercapacitors achieved an energy density of 114.49 μWh·cm^-2 at power density of 4001.59 μW·cm^-2 and a power density of 24000 μW·cm^-2 at energy density of 80 μWh·cm^-2.

Key words: zinc cobaltate, ammonium fluoride, areal capacitance, asymmetric supercapacitors