| Nano-science and technology are advanced and novel techniques in 21 century. Nano-material is an important part of nano-science and technology. The special structure and specific property of nano-particles make it different from traditional materials. It is springing up that people explore nano-science and technology.There are two parts in this thesis. The first section: The preparation of nano-Ni(OH)2 in the presence of PEG surfactant and study of its electrochemical performance. The second section: Study on the modified alkaline MnO2 electrode doped with nanosized composite oxide.In the first section, Ni(OH)2 powders were prepared by the different methods of solid-state reaction, organic liquid-phase reaction and organic compound-water solution reaction, respectively..1. TEM shows all samples are nanosized particles and their dispersion become better with the increase of amount of PEG surfactant. And have the same single size.2. XRD analysis showed nano-samples prepared by solid-state reaction and organic liquid-state reaction are sα/β -Ni(OH)2- And the percentage α-phase increases with the increase of PEG surfactant. But the crystallity of the powders is poor, low density and loose. The nano-samples synthesized by organic compound-water solution reaction are P -Ni(OH)2, crystal property and density are improved.3. Nano-Ni(OH)2 composite were prepared with doping metal ions. The synthesized samples were characterized by TGA, IR, XRD techniques. The results showed that the percentage of water and anion increase among Ni(OH)2 slabs due to layered the structure dopantion high valence metal ion. The α- Ni(OH)2 were produced in the samples.4. Electrochemical measurements showed that nano-powders prepared by different methods had different activity nano-Ni(OH)2 prepared by organic compound-water solution reaction, have an excellent electrochemical performance is excellent such as larger capacity, better reversibility, longer life, and higher reduction potential (ER). The largest discharge capacity is 279mAh/g, and the utilization of active material reach 96.5%.5. The cyclic voltammetry experiments indicated that there was a certain relation between ER and Z/r (Z, r is valence and radius of doped positive ions in the charge process,respectively.). When Z/r is larger, ER is larger, too. An experimental formula was summarized: ER1 - 1000(A1A2) + 100sgn([100A2] -[100A,])=ER2 where ER1, ER2, A1, A2 are sample 1,2 ER and Z/r of doped positive ions in the charge process. Calculation showed that PEG surfactant has an effect on calculative error. The influence increases with the increase of PEG. It is effect by special adsorption and coordination with metal positive ions.In the second section: 1. Bi-Ni composite oxide was prepared by solid-state reaction. It is characterized by physical and electrochemical techniques. The results are as following:1. XRD analysis showed that it consist of β -Bi2O3 (Tetragonal) and NiO (Rhombohedral) with mixing in 1:2 Mole ratio. Its nano-particle diameter is 9nm.2.Galvanostatic discharge experiments indicated nano-Bi-Ni composite oxide made up electrode, which had lower voltage plateaus and capacity. When it was mixed with y -MnO2 (I.C.No. 1) in different ratios, it could only improve deep discharge capacity.3. The discharge capacity could be increased when MnO2 electrode doped with nano-Bi-Ni composite oxide <35% under 8mA. The effect of modified alkaline MnO2 electrode showed that the best doped amount was in a range of composition (0%-5%). The discharge capacity was increased about 35% and 42.7% with 8mA and 6mA discharge respectively. In addition, the discharge plateau descended with the increase of nano-Bi-Ni composite oxide substitution. The improved efficiency of capacity reduces, too. So dopantion should be controlled little amount doped (≤2.6%).4. The cyclic voltammetry experiments indicated that nano-Bi-Ni composite oxide would change reaction path and process of redox stages of MnO2in deep discharge region. It stabilized the st...
|
PDF Full Text Request