Fabrication Of Metal Compounds On Porous Metals And Three-dimensional Graphene For Supercapacitor

With the rapid development of miniaturized and wearable electronic devices,a great deal of effort has been devoted to the research and development of supercapacitors with high energy density.The integrated electrodes with free-standing3D porous conductive current collectors and nanostructured metal compound combined have exhibited great potential in the field of supercapacitor energy storage because of their excellent electrical conductivity,large active surface area and high mass loading of active materials.However,these problems,such as large and uncontrollable pore size,low mass loading of active materials and low packing density,lead to poor space utilization and low overall performance of integrated electrodes,limiting their wide application.Therefore,it is of great significance to develop integrated electrodes with controlled pore structure and superior space utilization.In this paper,3D porous Ni-Co film,N-doped 3D rivet graphene and their composites were successfully fabricated by annealing,chemical vapor deposition?CVD?and hydrothermal processes,using nanoporous metal as the substrate.The effects of CVD parameters,pore size and hydrothermal time on the morphology and structure of as-fabricated samples were systematically investigated.In addition,the electrochemical properties and interaction mechanism of the composites were also investigated.The 3D porous Ni-Co film?3DNC?with high specific surface area,excellent electrical conductivity and reasonable pore size was obtained as a substrate to deposit vertically arranged CoMoO₄ nanosheets via hydrothermal and low-temperature annealing processes.The dense CoMoO₄ nanosheets almost completely fill the pores of the 3DNC film,effectively increasing the mass loading of active material and maximizing the space utilization of the integrated electrode.Owing to the rational structure design and efficient synergistic effect between CoMoO₄ and 3DNC film,the CoMoO₄/3DNC film electrode exhibits ultrahigh specific capacitance(2601.3 F cm^-3,325.2 mAh cm^-3),excellent rate performance and ultralong cycle stability(89.6%capacitance retention after 20000 cycles at 400 mA cm^-2).Free-standing N-doped 3D rivet graphene?N-3DRG?film with excellent conductivity,low quality,high hydrophilicity,high specific surface area and micron-sized interconnected pore structure was successfully synthesized by using the combination of pre-calcination and CVD,and then it was used as the substrate for the deposited of ultrafine Ni?OH?₂ nanoneedles?Ni?OH?₂/N-3DRG?.The introduction of N element effectively improves the wettability between the N-3DRG film and the metal compound,and makes the Ni?OH?₂ nanoneedles densely and stably arranged on the inner and outer surfaces of N-3DRG,effectively reducing the volume and weight percentage of the carbon matrix in the overall composite.Therefore,the(Ni?OH?₂/N-3DRG film achieves high specific capacitance of 1844 F g^-1(256.1 mAh g^-1).Furthermore,the as-fabricated Ni?OH?₂/N-3DRG based ASCs exhibit superior energy density(50.8 Wh kg^-1)and relatively good cycle stability.