| The ever worsening energy depletion and global warming issues call for not only urgent development of clean alternative energies and emission control of global warming gases, but also more advanced energy storage and management devices. Supercapacitor has already become one of the rese arch interests related to new chemical energy sources studies due to its higher energy density than secondary batteries and higher power density compared to conventional electrical double-layer capacitors. Nevertheless, the performance, cost and cycle life of supercapacitors are largely determined by the structure and electrochemical activity of the electrode. Therefore, many efforts are focused on the development of electrode materials with high capacity and environmental friendliness at present.In the thesis, we have reviewed the newest development in the research of electrode materials of supercapacitor devices. In particular, Ni(OH)2 was also introduced in detail due to its intense applications as an attractive candidate for supercapacitor. Our work was primarily focused on the optimization and modify of the electrode materials. The main results are as follows:1. Ni(OH)2 was directly electrodeposited at different electrodeposition temperatures. The effect of the electrodeposition temperature on the crystalline structure, morphology, specific surface area and electrochemical performance of Ni(OH)2 electrode was also systematically investigated. The results demonstrated that the electrodeposition temperature had obviously affected the properties of the Ni(OH)2. When the temperature is 65℃, the specific capacitance of the sample was up to 3357 F g-1 at a charge-discharge current density of 4 A g-1. Moreover, an asymmetric supercapacitor based on the Ni(OH2 sample as positive electrode and activated carbon as negative electrode has been fabricated and tested in 1 M KOH. The asymmetric device exhibits the energy density of 37.14 Wh kg-1 at the power density of 387.5 W kg-1, which suggests its potential application as an electrode material for supercapacitors.2.3D Ni-Co layered double hydroxides with different content of Co were successfully prepared via the co-electrodeposition method. The effect of the Co/Ni molar ratio on the crystalline structure, morphology and electrochemical performance of Ni-Co layered double hydroxides was also throughly investigated. It was found that the Co/Ni molar ratio had a significant influence on the crystalline structure, morphology and electrochemical performance of the as-synthesized materials. Moreover, an asymmetric supercapacitor based on the NiCoOH2 sample as positive electrode and activated carbon as negative electrode has been fabricated and tested in 2 M KOH. The asymmetric device exhibits an outstanding energy density of 53.98 Wh kg-1 at the power density of 71 W kg-1.3. Based on the above work,3D Ni-Co layered double hydroxides were calcined at 300"C for 2 h with a ramping rate of 1℃min-1 to prepare NiχCo1-χ oxides. As a result, the crystalline structure, morphology and electrochemical performance of 3D NiχCo1-χ oxides can be readily manipulated by simply varying the Co/Ni molar ratio in the electrodeposition electrolyte. However, the Ni0.61Co0.39 oxide electrode shows a large specific capacitance of 1523.0 F g-1 at 2 A g-1 and 95.30% of that can be retained even at a high current density of 30 A g"1. Moreover, an asymmetric supercapacitor based on the Ni0.61Co0.39 oxide electrode as positive electrode and activated carbon as negative electrode has been fabricated and tested. The asymmetric device delivers a prominent energy density of 36.46 Wh kg-1 at the power density of 142 W kg-1, which will hold great promise in potential application for energy storage. |
PDF Full Text Request