The Study Of The Electrochemical Performance Of Hydrazine Reduced Graphene Oxide And ? Ni-Co Hydroxides Forsupercapacitors

In recent years, supercapacitors(also known as electrochemical capacitors) have attracted extensive research interests in the domestic and overseas because of their high power density and long cycle stability, which has broaden their application prospects in the field of power electronics, electric vehicles and portable electronic equipments. This new high-performance supercapacitor is depending on the research of the electrode active materials. On account of the special layered structures and good electrochemical properties, the two-dimension reduced grapheme oxide nanoflakes and the bimetallic nickel cobalt-based hydroxides have been gradually applied in the study of the supercapacitor electrode active materials. In this paper, the preparation methods, the morphologies and electrochemical properties of these two materials were deeply investigated. And the relationship between the structure of the active material and electrochemical properties was discussed. The main results of this study are as follows:The two-dimensional graphene oxide nanoflakes GO were prepared by an improved Hummers method, and followed by the hydrothermal hydrazine reduction, the reduced graphene oxide, rGO was successfully obtained. Some surface analysis techniques such as XRD, Raman spectroscopy and FT-IR were applied to detect the structural features of rGO, and it was found that the rGO surface contain many oxygen-containing groups and a large number of structural defects, and the adding amount of hydrazine has a great impact on the disorder of its surface. In the electrochemical performance analysis, both of GO and rGO displayed a typical electric double layer capacitance. Moreover, the rGO active materials exhibited better electrochemical properties than GO. And the adding amount of the hydrazine showed a good effect on the electrochemical capacitance, when the amount of hydrazine added in the experiment is 0.6 mL, r GO displayed a high specific capacitance of 207 Fg-1 at a current density of 1 Ag-1.A simple precursor conversion method was proposed to successfully prepare ?-phase bimetallic nickel-cobalt hydroxide materials with different nickel and cobalt components but similar morphologies. The obtained materials have unique nanosheet structure and excellent redox activity. Compared to the nickel hydroxide, the introduction of cobalt ions was beneficial for the improvemrnt of the cycling life, the specific capacitance and the rate capabilityof the Ni-Co hydroxides. When the molar ratio of nickel and cobalt is 1:1, Ni0.5Co0.5 hydroxide deliver a high specific capacitanceof 1600 Fg-1at the current density of 1 Ag-1, and the capacitance of Ni0.5Co0.5 hydroxide could still retained at 100% of the initial specific capacitance after 1000 GCD cycles at a high current density of 10 Ag-1. The relationship between the remaining interlayered glycol molecules with the long cycling life of nickel-cobalt hydroxide was further investigated by the Fourier Transform Infrared(FT-IR) technique. Since the introduction of cobalt ions stabilize the glycol molecules in the interlayer, which effectively suppressed the transformation of nickel-cobalt hydroxide from ? phase to ? phase, resulting in higher stability for the active materials.