Preparation And Characterization Of Nanoarrays Electrode Based On Co-Ni Compounds

Supercapacitors?SC? play an enormous role in the species of energy storage system, which are benefit from the excellent advantages such as high energy density, power density and long cycle life. Both electric double layer capacitors and pseudocapacitors are supercapacitors, and the difference is due to their work mechanism. Pseudocapacitors can output higher effciency than electric double layer capacitors because the redox reactions completed both surface and internal of the electrodes. However, pseudocapacitive materials exhibit poor electrical conductivity which restrict ions and electron transport towards their theoretical capability. It is exactly based on the point that to overcome the problem that we designed highly conductive three-dimensional?3D? nanostructured arrays for loading more active materials. Highly conductive nanostructured arrays scaffold can facilitate electron transport and electrolyte diffusion, and thus enhance the electrochemical performance. To further improve electrochemical performance, we also doped the gold particles into manganese dioxide to improve the electrical conductivity of pseudocapacitive materials. In addition, we also designed three-dimensional?3D? nanostructured nitrogen-doped carbon nanotube?NCNT? to load materials.At first, we constructed three-dimensional porous Co_xNi_1-xO nano tube as the scaffold to load electrode active materials. Subsequently, we coat MnO2 out of Co_xNi_1-xO NT with the same time we incorporated Au nanoparticles. In order to characterize the lattice structure of the composite material Au-MnO2/Co_xNi_1-xO NT, we provided XRD and XPS characterization. The discharge areal capacitance of the Au-MnO2/Co_xNi_1-xO NT?1.390 F/cm2 at 1 mA/cm2? is 2 times as that of the MnO2/Cox Ni1-xO NT?0.601 F/cm2 at 1 mA/cm2?. The Au-MnO2/Cox Ni1-xO NT electrode exhibits a smaller Rct?7.8 ?? than that of MnO2/Co_xNi_1-xO NT?20.30 ??, indicating more effcient electrolyte discusion. Besides, the Au-MnO2/Co_xNi_1-xO NT exhibits excellent cycling stability with high capacitance retention of 95.4% after 5000 charge/discharge cycles at a current density of 8 mA/cm2.Furthermore, the composition and structure of electrodes are two key factors to determine the electrochemical performance. Herein, we report that a novel mixed metal selenide in the formula of Co_xNi_1-xSe₂ is successfully attached on the surface of nitrogen-doped carbon nanotube?NCNT? via the electro-deposition and subsequent selenization processes, forming the coaxial Co_xNi_1-xSe₂/ forest. Co_xNi_1-xSe₂/NCNT forest as three dimensional self-supported electrode shows the remarkable electrochemical performance, of which an areal capacitance is achieved to 5.9 F/cm2 at 2 mA/cm2, and is 2, 13, and 17 times as that of Co_xNi_1-x?OH?2/NCNT, Co_xNi_1-xSe₂, and Co_xNi_1-x?OH?2, respectively. The enhancement in electrochemical performance is ascribed to the increased mass loading and the improved electron and electrolyte transport characteristic via loading high performance electroactive materials on a three dimensional NCNT forest scaffold. Additionally, FeOOH also can be electro-deposited at the surface of NCNT to form FeOOH/NCNT as the negative electrode, integrating with Co_xNi_1-xSe₂/NCNT to form the asymmetric cell?AC?. The AC delivers a high volumetric capacitance of 12.3 F/cm3 at 4 mA/cm2, and has a good cycling stability with 86 % retention after 10000 cycles.