| In recent years,supercapacitors,as new type of energy storage devices,have developed rapidly.The research on the preparation methods and properties of electrode materials,which is one of the decisive factors in the performance of supercapacitors,has become the primary goal of scientific development.Manganese dioxide,as the cathode material of supercapacitor,has the advantages of rich resources,friendly environment and high theoretical capacitance,which has been widely concerned and explored.However,as a single electrode material,it still has obvious deficiencies in capacitance and stability.In order to solve thiese problems,a kind of porous core-shell cathode material was designed and prepared in the present work,The structure,morphology,chemical composition,and electrochemical performance of the material were analyzed and discussed in detail by XRD,FE-SEM,TEM,XPS,and electrochemical testing methods.At the same time,the formation mechanism of core-shell structure was studied and analyzed.It is proved that the electrode material with special structure can make use of synergistic effect to improve and improve the electrochemical performance.The main research contents are as follows:Here,the porous flower-shaped core-shell structure Co3O4@Mn O2 cathode materials were prepared by hydrothermal method under the experimental conditions hat the ratio of urea and cobalt chloride was 1:5 and the hydrothermal temperature was 160°C for 6 hours.Furthermore,Co3O4@Mn O2@PPy positive materials with highly conductive PPy shell as the casing were prepared by electrodeposition method.The electrochemical test shows that the specific capacitance and the corresponding capacitance retention rate of Mn O2,Co3O4@Mn O2 and Co3O4@Mn O2@PPy positive materials increase in turn at the current density of 1 A·g-1with the best electrochemical performance has a specific capacitance of 977F·g-1,a capacitance retention rate of 105%,and a charge transfer resistance of 1?.After a series of discussion and analysis,it can be seen that the growth mechanism of the porous core-shell structure is"dissolution-nucleation-growth-Ostwald ripening mechanism".This porous core-shell structure has a large contact surface area and the distance between each nanoneedle enhances the diffusion power of the endoplasmon of the electrode and ensures the effective contact between the electrode and the electrolyte,thereby the electrochemical performance is significantly improved owing to the increasing reaction rate of the active substance.The electrochemical performance of Co3O4@Mn O2@PPy//AC asymmetric supercapacitor assembled with AC as the negative electrode material is significantly better than that of Mn O2//AC and Co3O4@Mn O2//AC.The capacity of Co3O4@Mn O2@PPy//AC is103 F·g-1,and the corresponding energy density and power density are 55.3 Wh·kg-1 and8589.3 W·kg-1,respectively.Moreover,the capacity retention rate is still 120%for 5000charge-discharge cycles.The experimental results show that the synergistic effect of the multi-component materials can significantly improve the electrochemical performance of the positive materials,which makes it have a certain practical value as a positive material of supercapacitor. |
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