Study On The Properties Of Iron-based Oxide Electrode Materials On Supercapacitors

Supercapacitor is a new type of energy storage device.It has the characteristics of fast charging speed and good temperature performance.It is expected to meet the energy storage requirements in future practical applications.Non-precious metals,such as iron,are abundant reserves,cheap and environment friendly.They have obvious advantages and wide application prospects in the field of supercapacitors.Iron-based oxides have many crystal morphologies,which make it possible to adjust and optimize their electrochemical properties.In this paper,iron-based oxide electrode materials and iron-carbon composite electrode materials have been studied,by optimizing the experimental methods and composition allocation.The structure and composition of the materials have been studied in detail.Higher specific capacitance and good electrochemical stability have been obtained.Firstly,Fe2O3@Ni electrode material was prepared by hydrothermal method.The result shows the surface products of nickel foam are composed of nanowires and cubic shape nanoparticles.The XRD result shows that the product is ?-Fe2O3,belonging to the three square crystal system.The results of electrochemical tests showes that in 1.0 mol L-1 KOH electrolyte system,Fe2O3@Ni electrode material exhibits pseudocapacitive property and good electrochemical activity.Fe2O3@Ni electrode exhibits a specific capacitance of 811.1 F g-1 at a current density of 1.0 A g-1.Compared with the non-in-situ Fe2O3 electrode,the specific capacitance increases by 93.0%.Fe2O3@Ni electrodes have smaller equivalent resistance and better ion transfer ability.After 5000 charge-discharge cycles,Fe2O3@Ni//AC asymmetric capacitor maintained 51.2%of the initial specific capacitance at 1.0 A g-1 current density.Secondly,Fe2O3-C@Ni electrode was prepared by one-step hydrothermal method.The effects of reaction temperature and molar ratio of iron to carbon precursor on the morphology,composition and activity of the product were investigated.The result shows that the surface products of nickel foam are composed of nanowires and nanosheets.The electrochemical test showed that the Fe2O3-C@Ni electrode exhibits pseudocapacitance.Fe2O3-C@Ni electrode exhibits a specific capacitance of 858.1 F g-1 at a current density of 1.0 A g-1.Compared with Fe2O3@Ni,the specific capacitance increases by 6.0%.After 20000 cycles,the specific capacitance retention can reach 79.2%.This result shows that the addition of carbon in Fe2O3-C@Ni electrode significantly improves the electrochemical stability of the electrode.Finally,active carbon(AC)as the negative electrode and Fe2O3-C@Ni as the positive electrode,Fe2O3-C@Ni//AC asymmetric capacitor was assembled.The electrochemical test shows that the maximum energy density of the capacitor can reach 54.7 W kg-1 in 1.0 mol L-1 KOH.The specific capacitance retention of asymmetric capacitors can reach 92.0%after 20000 charge-discharge cycles in 6.0 mol L-1 KOH electrolyte solution.In conclusion,Fe2O3-C@Ni electrode material has good energy density and electrochemical stability.