Preparation And Electrochemical Properties Of Nickel-cobalt-manganese-based Electrode Materials

As a device with excellent energy storage capacity,supercapacitors are widely used due to their long cycle life and fast charge/discharge advantages.The electrode material is an important factor affecting the performance of supercapacitors.Transition metal hydroxides and oxides are potential electrode materials for supercapacitors due to their high specific capacity,low cost and environmental friendliness.In this thesis,two electrodes,Ni-Co LDH/NF and Ni-Co LDH/Mn₃O₄/NF,were prepared by constant pressure electrodeposition on the surface of nickel foam substrate,and the electrochemical properties of both were tested as well as the physical properties such as phase structure,elemental composition,chemical state,and surface structure were characterized.The main findings of the study are as follows:(1)The electrochemical performance of Ni-Co LDH electrode was studied under the optimal preparation experimental conditions of nickel chloride concentration 10mM,cobalt nitrate concentration 5 mM,reaction time 300s and deposition temperature 25?,and the specific capacity was 2357 F/g when the current density was 1 A/g.At the current density of 10 A/g,25?,after 3000 times of continuous charge and discharge,the capacitance retention rate is 81.8%.Since the weakly crystalline Ni-Co LDH electrode material has a sheet grid structure,it can provide more ion and electron transport channels and has a lower ion transport resistance,which is conducive to the redox reaction and thus improves the electrochemical performance of the electrode.(2)The electrochemical performance of Ni-Co LDH/Mn₃O₄/NF electrode was studied under the experimental conditions of optimal preparation of nickel chloride concentration 10 mM,cobalt nitrate concentration 15 mM,manganese acetate concentration 15 mM,reaction time 300s and deposition temperature 45°C.The specific capacity was high when the current density was 1 A/g,which could reach2680 F/g.With the addition of Mn elements,the electron binding energy of Ni and Co decreases and the electronic state changes,indicating that there is a strong electronic interaction between the compounds in the Ni-Co LDH/Mn₃O₄/NF electrode,and it is the existence of the synergistic effect that can further improve the electrochemical performance of the electrode.(3)The cycling performance of the Ni-Co LDH/Mn₃O₄/NF electrode was tested in 2 M KOH electrolyte at a current density of 10 A/g,and the specific capacity retention rate was 85.6%after 3000 consecutive charges and discharges.Characterizing the physical properties of the electrode after conducting the cycling performance test,it was found that the changes in the electronic state of the electrode material elements and the surface microstructure were the reasons why the cycling stability did not reach 100%.Meanwhile,the continuous charging and discharging of the electrode is a reversible redox reaction,and there are obvious charging and discharging voltage plateaus in the test curve,which indicates its pseudo-capacitance energy storage mechanism and shows that the electrode has a good energy storage capacity.