Preparation And Properties Of α-Fe₂O₃/Graphene Hydrogel Composites As Anode Materials For High Performance Asymmetric

The rapid development of various portable electronic devices,hybrid electric vehicles,and aerospace industry greatly boosts the demand of high-performance,cost-effective,and environmentally friendly energy storage devices.As an emerging power source,supercapacitors have attracted wide attention in various fields due to their high power density,good cyclic stability and rapid charging and discharging process.However,its low energy density seriously hinders its commercial application.Therefore,the design and assembly of asymmetric supercapacitors to maximize the voltage window and energy density has become the main research direction of supercapacitors in recent years.Although there have been a lot of researches on asymmetric supercapacitors（ASCs）,the anode materials are still mainly carbon-based materials.However,the carbon-based materials with humble specific capacitances cannot match the cathode materials,limiting the energy density of ASCs.In this paper,we have developed a cost-effective and environmental-friendly anode of homogenousα-Fe₂O₃nanoparticles grown on three-dimensional graphene hydrogel（α-Fe₂O₃/GH）,which possesses a high specific capacitance of 789 F/g at 1 A/g and excellent cycling stability（82%of capacitance retention after 5000 cycles）.The composite material of NiCo₂O₄nanorods grown on 3DG（NiCo₂O₄/GH）has been prepared as the cathode by a similar method.The NiCo₂O₄/GH also shows great electrochemical performance（1264 F/g at 1 A/g and 92%of capacitance retention after 5000 cycles）.Furthermore,the ASCs of NiCo₂O₄/GH//α-Fe₂O₃/GH,which is composed of the as-prepared cathode and anode materials,exhibits the high energy density of 78 W·h/kg at the power density of 800 W/kg and outstanding cycling stability（81%of capacitance retention after 5000 cycles at 10 A/g）.The excellent electrochemical performance ofα-Fe₂O₃/GH anode in ASCs promotes the practical application for the development of high-performance supercapacitors.