Preparations Of Nickel-based Nanocompound/Carbon Cloth Composite Electrode Materials And Studies Of Their Electrochemical Capacitive Properties

Supercapacitors, with its excellent performance of high power density, long cycle life, fast charge and discharge and high safety, have attracted much attention. Especially in recent years, the rapid development of portable equipment makes us to pay more attention to smaller and more integrated and portable supercapacitors. However, most present supercapacitors and electrode materials are lacking of flexible characteristics. Moreover, only a few supercapacitors available now are satisfied with the demand of industry. Thus, in this thesis, three kinds of Ni-base nanocompound/carbon cloth composite electrode materials had been fabricated by means of hydrothermal synthesis method and annealing treatment. Besides, two kinds of symmetrical supercapacitors were assembled. Their structures and performances were characterized. The detailed research content as follows:1.Ni（OH）₂/carbon cloth had been fabricated via hydrothermal process to be the precursor, which was then calcined under air at different temperature to achieve the NiO/carbon cloth composite electrode material. The structure and performance were studied. The results showed that the crystallinity of NiO nanoneedle in composite electrode material obtained at 500 ℃ was the best. The electrochemical results suggested that NiO/carbon cloth possessed an excellent electrochemical capacitance of 300.4 mF/cm2 at current density 5 mA/cm2. What was more, after 3000 cycles of galvanostatic charge-discharge tests, the capacitance retention of the NiO/carbon clothelectrode still retained 81.5%.2.NiNiCo₂O₄/Carbon clothelectrode had been fabricated via hydrothermal method and calcined under air. Then, this electrode was used as precursor to obtain NiCo₂S₄/carbon cloth electrode by further hydrothermal process, ion exchange method and calcination under nitrogen atmosphere. The structure and performance were studied. The results showed that the specific capacitance of NiNiCo₂O₄/carbon cloth was far less than that of NiCo₂S₄/carbon cloth. However, the cycle stability of the former is far more excellent than that of the latter. The stability of NiNiCo₂O₄/carbon was good and it exhibited electrochemical capacitance of 348.5 mF/cm2 at current density 3 mA/cm2. After 10000 cycles, the capacitance retention of NiNiCo₂O₄/carbon cloth was 81.9%.3. The NiO/carbon cloth and NiNiCo₂O₄/carbon cloth had been designed and assembled into symmertrical supercapacitors, respectively. The performancef of the symmertrical supercapacitors were investigated. For NiNiCo₂O₄/carbon, the symmetric supercapacitor had capacitance retention of 92.7% and coulombic efficiency of 107% after 23000 cycles under the current density of 0.8 mA/cm2. For NiO/carbon cloth, the symmetric supercapacitor showed capacitance retentionof 91.4% and coulombic efficiency of 96.8% after 15000 cycles under the current density of 1.0 mA/cm2. Under the normal state of bending and distortion, the capacitances, electric conduction abilities and charge-discharge performances of the two devices nearly remained unchanged.