Ribbon Graphene/Metal-Based Pseudo-Capacitor Materials For Asymmetric Supercapacitors

The energy crisis has promoted the development of supercapacitor devices,but the low energy density has limited their applications.Designing and developing electrode materials with high specific capacitance,as well as assembling asymmetric supercapacitors to further expand the working voltage,can help further break through the energy density limitations of supercapacitors.Metal pseudocapacitive materials have high theoretical specific capacity,but their conductivity and cycling stability are poor.In response to this issue,this article combines metal pseudocapacitance materials with strip graphene materials,and further enhances the stable binding between metal pseudocapacitance materials and strip graphene materials by adjusting the content of oxygen-containing functional groups on the graphene layer,thereby improving the electrochemical performance of the composite materials.The specific research content includes the following two aspects:（1）The IGO/Mo S₂ and IGO/Mn O₂ composites were prepared by growing Mo S₂and Mn O₂materials respectively on the banded graphene（IGO）surface by"spray rapid freezing"and hydrothermal in-situ growth methods.On the one hand,the strip structure of IGO increases the edge active sites of graphene,which is conducive to the growth of Mo S₂ and Mn O₂ on the graphene surface.Secondly,IGO with good conductivity makes up for the poor conductivity of Mo S₂ and Mn O₂,which is conducive to improving the conductivity of IGO/Mo S₂ and IGO/Mn O₂ composites.On the other hand,the formation of banded graphene coated Mo S₂ and Mn O₂ structure not only inhibits the aggregation of Mo S₂ and Mn O₂,but also prevents the volume expansion of Mo S₂ and Mn O₂ during the electrochemical cycle process,which is conducive to the enhancement of the rate performance and cycling ability of IGO/Mo S₂ and IGO/Mn O₂ composites.An asymmetric supercapacitor assembled with IGO/Mn O₂ as the positive electrode material and IGO/Mo S₂ as the negative electrode material has an energy density of 62.6Wh kg^-1 and a power density of 250.5 W kg^-1.（2）In order to better combine IGO with metal pseudocapacitor materials,oxygen-containing functional groups are introduced on IGO to prevent shedding in the electrochemical cycle process.By adjusting the oxygen-containing functional groups content of IGO（oxidizing IGO（OIGO）and reducing IGO（RIGO））,Ni（OH）₂ and Fe₂O₃were combined,respectively,and the effects of the content of different oxygen-containing functional groups of IGO on the binding stability and electrochemical performance of pseudocapacitor materials were studied.The research shows that OIGO/Ni（OH）₂ and OIGO/Fe₂O₃ have achieved good electrochemical performance.Because oxygen-containing functional groups can provide active site and combine more pseudocapacitive materials,it is conducive to improving the specific capacity of composite materials.OIGO/Ni（OH）₂and OIGO/Fe₂O₃ are used as positive and negative electrodes to form an asymmetric supercapacitor,which has good electrochemical performance.The asymmetric supercapacitor has an energy density of 92.8 Wh kg^-1and a power density of 417.4 W kg^-1.