Facile Synthesis of Ni/Co (Hydr)oxides with Nanosheet Structure for High Performance Supercapacitors

In this article, the novel kind of binary metal oxides, Ni/Co (hydr)oxides, with nanosheet structure have been successfully established via a facile hydrothermal self-assembled process with ammonia solution as the reaction reagent. The as-prepared samples with peculiar morphologies and characteristics are easily realized by just controlling the calcination temperatures. The composition, morphology, and microstructure of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The thermogravimetric analysis (TGA) revealed the decomposition details of the precursor. Electrochemical measurements show that the sample calcined at 250°C has the optimized capacitive performance, demonstrated by cyclic voltammetry and galvanostatic charge-discharge cycling techniques. The Ni/Co hydroxide nanosheets as electrode materials for supercapacitor exhibit high specific capacitance of 1427 F g -1 at 1 A g -1 , and 1270 F g -1 at 10 A g -1 , indicating an excellent rate capability. Also, the superior cyclic stability with the capacitance retention of 92.3% is achieved even over 3000 cycles at a high current density of 10 A g -1 . The improved capacity and cycling stability makes it promising electrode material for offering an effective way to achieve high supercapacitor performance.