Abstract:

In this work, the flake nickel cobalt hydroxide was successfully prepared by the chemical co-precipitation method, and the effect of nickel to cobalt molar ratios on the morphologies and electrochemical properties were explored. The structures and morphologies of samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscope (XPS) and specific surface area and pore size analyzer (BET). The electrochemical properties were analyzed by cyclic voltammetry, galvanostatic charge/discharge, etc. The results show that when nickel cobalt hydroxide (n(Ni):n(Co)=4:1) is directly used as electrode material, it has a high specific capacitance of 1852 F/g at a current density of 0.5 A/g. When the current density is increased by 20 times, it still has a high specific capacitance of 1330 F/g. The asymmetric supercapacitor is assembled with nickel cobalt hydroxide as the positive electrode material and active carbon as the negative electrode material. The asymmetric cell possesses a high energy density of 52 Wh/kg at a power density of 346 W/kg, and superior cycle stability (the capacitance retention of 92% after 10000 cycles). Excellent electrochemical properties indicate that flake nickel cobalt hydroxide is one of the most promising electrode materials.

Key words: nickel cobalt hydroxide, supercapacitors, cycle stability