| Supercapacitor is a kind of energy storage device. Its principle is based on the electrochemical process of electrode / solution interface. It not only has the energy storage capacity which can be comparable to the battery, but also has the discharge power which is as large as the electrostatic capacitor. Because of many outstanding advantages, supercapacitor attracts the attention from all over the world and becomes the research focus. The electrode material is one of the key factors affecting the performance of supercapacitor. Due to so many advantages, such as low cost, easy to synthesis, friendly to the environment and high theoretical specific capacitance of 2584F/g, Ni O is considered as an ideal electrode material which is most likely to be applied in actual situations. Therefore, researchers pay great attention to it. The conductivity of nickel oxide is relatively poor and the migration velocity of ion in the electrolyte is slow, resulting in low availability of Ni O. Therefore, in this thesis, Ni O nano tube doped with materials with good conductivity can be prepared by electrospinning method. Thus, the specific surface area and conductivity can be increased so as to further improve the electrochemical performance of the prepared electrodes.By using the electrospinning method, the lanthanum doped Ni O electrodes with hollow structure were prepared, with the molar doping ratio of La:Ni=0:1,1:1,1:2,1:4. When the electrochemical performance of prepared electrodes were tested in 7mol/L KOH electrolyte, it can be found that when the ratio is La:Ni=1:2, the best ratio and the best electrochemical performance were obtained. It showed a remarkable specific capacitance of 257.8F/g scaled the total mass of the electrode, or 942 F/g scaled to the active mass(Ni O) at the current density of 0.5A/g The value is 14 times higher than that(70.5 F/g) of the pure Ni O sample.The cycling test suggested that the electrode had excellent cycling performance, with only 10% capacitance loss after 1000 cycles.Using the preparation process of electrospinning, the Ag-doped Ni O hollow nano fibers with high specific surface area were prepared. The doping ratio of Ag NO3: Ni2+ salt was 1%, 2.5%, 5%, 10%(mass ratio). The analysis on morphology, crystal structure, specific surface area and pore diameter was performed systematically and separately. When the electrochemical performance of the electrodes was tested in the 7mol/L KOH electrolyte, it can be found that when the mass ratio of Ag NO3 to Ni2+ salt in the raw material is 5%, the best electrochemical performance can be achieved. The capacitance can reach 200F/g at the current density of 0.5A/g. The capacitance retention rate can maintain 95.6% after the charge-discharge tests for 1000 times. It also showed a good conductivity, with the Faradic resistance of 2.59?.According to the previous experimental results, the Ag-doped Ni O/La Ni O3(La:Ni=1:2) in different proportion of electrodes were prepared by using electrospinning method. The doping ratio of Ag NO3:(Ni(NO3)2+La(NO3)3) was 1%, 2.5%, 5%, 10%. By changing the content of silver, composite nanofibers with different contents can be obtained. When the electrodes were tested in the 7mol/L KOH electrolyte, it can be found that when doped ratio of Ag NO3 is 5%, the best ratio and the best electrochemical performance can be obatained and this doping method is superior to the first two methods. The specific capacitance can be up to 385.7 F/g at the current density of 1A/g. There is only 3% capacitance loss after charge-discharge test for 1000 times. The conductivity is greatly improved and the Faradic resistance is 0.79?. |
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