Preparation Of Hematite-Based Composites And Its Application In Supercapacitors

Abstract:Supercapacitor materials not only require abundant material sources,low prices,and environmental protection,but also require excellent electrochemical performance.Iron oxide（Fe₂O₃）is a good electrode material for supercapacitor due to its unique advantages,but its poor conductivity severely restricts its application in supercapacitor.Therefore,this article aims to improve its electrochemical performance through two aspects:metal ion doping to improve its intrinsic conductivity and combine with carbon nanotube（CNT）to enhance its apparent conductivity.The research content of this paper is as follows:（1）The composite of Ni²⁺-doped Fe₂O₃（Ni-Fe₂O₃）was prepared by calcining metal organic framework（MOF）precursors.The optimal synthesis time and doping ratio of Ni-Fe₂O₃composite are then explored.It found that under the conditions of a solvothermal reaction time of 15 h and a doping molar ratio of 9:1（Fe:Ni=9:1）,the Ni-Fe₂O₃composite has a larger specific surface area and better electrochemical performance.Through electrochemical tests,it found that compared with Fe₂O₃,the specific capacitance and rate performance of Ni-Fe₂O₃composite have been improved.It has a larger specific capacitance of 713.8 F g^-1F g^-1at2 A g^-1and at 10 A g^-1the rate capability of Ni-Fe₂O₃composite is 43.4%which is much higher than that of undoped Fe₂O₃（29.6%）.It shows that Ni-Fe₂O₃composite is expected to be used in supercapacitors.（2）In order to improve the performance of Fe₂O₃more comprehensive,this chapter combines the two methods of doping with transition metal ions and adding conductive materials,and successfully prepared the metal ion-doped Fe₂O₃/CNT composite material through the one-step hydrothermal method.Analyzed the test results,it found that the specific capacitance of the Fe₂O₃electrode material composited with CNT is about twice than that of a single Fe₂O₃,but its specific capacitance(141.3 F g^-1)cannot meet practical applications.In addition,the surface of the composited Fe₂O₃material becomes rougher and doping with metal ions（Mn,Ni and Co ions）can further improve the electrochemical performance of Fe₂O₃.Among them,the Mn-doped Fe₂O₃/CNT（Mn-Fe₂O₃/CNT）electrode showed the best performance.It has a high specific capacitance(742.6 F g^-1)at 2 A g^-1which may be due to the well contact with the electrolyte with the rough surface of the active material.Besides,even at 15 A g^-1,the capacity retention of 63.3%was achieved for Mn-doped Fe₂O₃/CNT.These suggested that Mn-doped Fe₂O₃/CNT was a promising candidate for supercapacitor electrode material.Choosing appropriate metal ions doping and combined with CNT can improve the electrochemical performance of Fe₂O₃effectively.