Study On Preparation And Properties Of Nb₂O₅ For Hybird Supercapacitor Anodes Material

In this paper,flower-like hierarchical Nb₂O₅ microspheres assembled by nanorod were prepared by hydrothermal method using NbCl₅,HO2CCO2H·2H2O and NH₄ F as raw materials.We have studied the effects of NH₄ F concentration,reaction temperature and reaction time on the structure and electrochemical properties of the electrode materials were studied.(Nb_1-xV_x)₂O₅ composite electrode materials were prepared by adding ammonium vanadate during the synthesis of Nb₂O₅ sample.Microstructure,electrochemical properity and kinetic characteristics of the cathode materials have been studied by means of XRD,SEM,EDX analyses and galvanostatic charge-discharge,CV and EIS.The results show that all the samples were Nb₂O₅ when the concentrations of NH₄ F is0.1 M,0.15 M,0.2 M and 0.3 M,respectively,but the morphoogy of the samples are different.The morphology of the sample presents flowe-like assembled by nanorod when the concentration of NH₄ F is 0.2M.The maximum discharge specific capacity of each concentration sample was 167.8 mAhg-1,168.2 mAhg-1?174 mAhg-1 and 155 mAhg-1 at the discharge cerrent density of 0.2 Ag-1and the voltage range of 1.0-3.0 v.The capacity retention was 73.4%,76.1%,93.5% and 69.2% after 50 cycles,respectively.The electrochemical performance of the samples was the best when the concentration of NH₄ F is 0.2M.The study of reaction time shows that the reaction time has no significant effect on the crystal structure between 12 hours and 20 hours,but crystallinity increases with the increase of reaction time.The test of electrochemical properity shows that the discharge specific capacities of the samples are about 12.7 mAhg-1,8.8 mAhg-1,162.7 mAhg-1,80.0mAhg-1after the cycle of 50 cycles,respectively,and the best electrochemical performance of the sample is18 h.The study of reaction temperature shows that the samples prepared at170 ? and 180 ? were Orthorhombic,the phase of the samples were transformed with the increase of reaction temperature.The rate performance of the samples shows decreasing trend with the increase of reaction temperature,The research on the doping of V shows that the maximum amount of vanadium /niobium molar ratio is 2: 5.The crystallinity of niobium pentoxide will change when it isgreater than this ratio.The maximum discharge specific capacity of samples for different vanadium/niobium ratios is 174.0 mAhg-1,176.0 mAhg-1,209.3 mAhg-1,230.8 mAhg-1,199.5 mAhg-1 and 174.5 mAhg-1,respectively.It can be found that the electrochemical cycle performance of the sample is the best when vanadium / niobium ratio is 1.5: 5 by compareing thesed datas,and the discharge capacity is still high after 50 cycles.EIS measurement indicates that the doping with appropriate amount of V decrease the charge transfer resistance.so the doping of vanadium is helpful to enhance the kinetic properties of Nb₂O₅.Hybrid supercapacitors were assembled using(Nb_1-xV_x)₂O₅ as negative and commercial activated carbon as positive electrode.The maximum energy density of this device is40.25 Wh kg-1,and its power density is 525 Wkg-1 under the operational voltage of 2.5 V.