Study Of Cobalt Doping Nickel Hydroxide/Nickel Oxide Anode Materials For Supercapacitors

Super capacitor have received widespread attention because of having a highercapacitance, higher energy density, power density, fast charge and discharge rate, andnon-pollution, etc.The electrode material as the decision of the main aspects of theperformance of the super capacitor, called the focus of the Supercapacitors field. Themore inexpensive and non-polluting hydroxides and oxides of nickel-cobalt-basedelectrode materials are researched more, they all have a higher capacitance, energydensity and power density, but because of its structural limitation, they tend to have alower conductivity and electrochemical stability, and effectively improving theutilization and retention rate of the electrode material by the method of introducing anadditive-modified.This thesis modifieding the character of the nickel-based hydroxide and its oxideby the introduction of the cobalt additives, there are three main significance. One is toimprove the conductivity of the material as a whole, thereby improving the utilizationrate of the electrode material, the second is to inhibit the forming of the γ-NiOOH,improving the chemical stability, At last Co can reduce the oxidation potential of thenickel, improve the nickel deposition potential, thereby enhancing the efficiency ofcharging and discharging of the capacitor.The experimental work of this thesis is prepared by different proportions ofnickel nitrate, cobalt-doped electrolyte by electrochemical deposition, preparingdifferent percentage content of the cobalt-containing Ni （OH）₂and NiO, then throughthe X-ray diffraction and sem method having a research on the microstructure andmorphology of the samples, and then they are studied by cyclic voltammetry andconstant current charging and discharging of the electrochemical properties of thesample analysis,at last we result in a conclusion.Nickel-based hydroxide when the Co content is50%, the continuity, the bindingand thickness of the sample are the best, and obtaining the ratio of the capacitance of1742F/g as measured in31.25A/g current density cycle, and constant current charging and discharging still achieve a retention rate of93%after500cycles, thecapacitance and the stability of the material are the highest. Nickel-based oxide whenthe Co content is100%, the distribution characteristics of the overall are the best andthe standing character of the nano petals increases,the phenomenon of falling could beeffectively improved, and in31.25A/g current density cycle the capacitor is257F/g,but it can still achieve100%retention rate after the constant current charge-dischargecycle4000times.In a word, nickel-based oxide electrode electrochemical properties are muchlower than the electrochemical properties of the nickel-based hydroxide, nickel-basedhydroxide electrode capacitance of cobalt content of50%can be achieved1800F/g ormore, much higher than the cobalt content of the nickel based oxide is260F/g;Overall retention rate of nickel-based oxide electrode are higher than the latter, theretention ratio of substantially nickel-based oxides thousand cycle still more times toachieve100%, the best retention ratio of nickel-based hydroxide is also only thecobalt content of50%, after500cycles it can be achieved93%retention ratio.