Preparation And Performance Characterization Of Co-based Electrode Materials For Supercarpacitors

Supercapacitors show an excellent application prospect in the field of electronic instructions and hybrid electric vehicles because of its high power density, good reversibility and outstanding cycle performance, etc. With good capacitive performance and environmental friendliness, cobalt compounds have become an important part of electrode material for supercapacitors. The electrode material of supercapacitor could be obtained by solvothermal method. However, from the reference, we can know that when using solvothermal method to prepare the cobalt oxide or cobalt hydroxide solvents, all methods of the references mix water with non-aqueous solvents according to certain proportion. But its properties are not studied in non-aqueous solvents. Therefore, we use it as our breakthrough point to explore the formation process of electrode material and its the electrochemical performance in the supercapacitor.We firstly use the simple solvothermal method to obtain cobalt hydroxide/cobalt oxide electrode materials, and further study its material composition, microstructure, electrochemical properties and a serial of problems using XRD, SEM, cyclic voltammetry, constant current charge-discharge, AC impedance, etc. This paper mainly studies the influence of reaction temperature and reactant concentration on the properties of electrode materials and furtherly explored the evolution of its morphology. The innovative result in the paper are as follows:(1) When the concentration of cobalt nitrate is 0.05 M, the crystal phase of the sample gradually transforms from lamellar α-Co(OH)2 to spherical structure Co3O4 phase with increasing reaction temperature. In addition, under higher reactant concentration or reaction temperature, the electrode material is easier to form spherical structure Co3O4 phase.(2) When the reaction temperature is 170°C and reaction concentration is 0.05 M, the micromorphology of the sample gradually transforms from the original lamellar-spherical structure to independent single lamellar structure. In addition, the morphology of the lamellar edges changes from the original smooth edges to angular-obvious state.(3) From our research, we know that the electrochemical properties of the electrode material are cooperative controlled by reactant concentration and reaction temperature. The most exceptional electrochemical properties appear when the concentration of cobalt nitrate is 0.1M and reaction temperature is 170°C. The corresponding specific capacitances in the current density of 1, 2, 5, 7, 10 and 15 A·g-1 are 594、510、433、396、368 and 336 F·g-1, respectively. From the above results, it is seen that when current density increases from 1 to 15 A·g-1, the specific capacitance still remains 56.6%, showing an excellent rate performance. In the density of 8 A·g-1, specific discharge capacity still remains 85.3% after 1100 cycles and the specific capacity reaches to 331 F·g-1, demonstrating outstanding cycle stabilities.