| As transition metal compounds,nickel sulfides,oxides and hydroxides own high electrochemiscal activity.In the energy storage aspects,these electro active materials can produce faradaic pseudocapacitance through the fast redox reaction on the electrodes surface and near surface location,can be used as supercapcitance electrode materials,which shows high theory speciafic capacitance that much larger than electrical double-layer capacitor.But the pure nickel compounds have several drawbacks no matter in morphology and structure,or in electron conductivity and electrochemical activity aspects,such as its wide energy gap limits the number of electrons carrers.While,these drawbacks can be overcomed after constructing nickel compounds based composites by taking advantage of their unique shapes,multifunctionality of each component,and controllability of building primary templates,meanwhile,the synergistic effect between the various phase that participate in the process of electrochemical reaction also has a great role in promoting the performance of the energy storage and conversion devices.In this paper,we studied the nickel-based composites for using as the supercapacitor electrode materials.By adjusting the nano/micron size of the materials,avoiding reunion,regulating the morphology and porosity,we tend to improve the electrical conductivity for high rate performance,long woking life and high power density of the supercapacitor electrode materials.The work in this paper is mainly focused on the following aspects:1.To avoid aggregation in the production of the active electrode material,Ni-Zn system materials(Nix Zn1-x OH and Nix Zn1-x S)were synthesized by a belt reaction zone model(modified interface method),and then were characterized systematically in this work.Low density and water-soluble N,N-Dimethylformamide(DMF)was used to replace the water-insoluble organic solvent based on traditional interface method,such as CCl4 and CH2Cl2,which bring several advantages compared with other interface methods: First,the sample synthesis reaction was controlled by double diffusion synergistic effects including ion diffusion and solvent diffusion,the confined belt reaction zone would effectively reduce the large-scale agglomeration and promote the synthetic efficiency;second,easy operating and no more organic addition agents were introduced;Third,the metal inorganic salts can be involved into reaction due to their good solubility in DMF.The as synthesized Ni1-x Znx OH samples possess super thin sheets which construct 3D net structure.After further sulfide,Nix Zn1-x S porous spheroid nanoparticles with diameters ~30 nm possess abundant interconnected microspores caused by Kirkendall effect in the synthesis,leading to a high surface area of 148.4 m2/g and special paths for ion diffusion.2.Multi-layers Nix Zn1-x S/Ni foam composites were synthesized by a facile method of one-step hydrothermal reaction on the frame of Ni foam.Zn element plays a critical role in constructing the multi-layers nanostructure.In particular,various layers with different morphology work in a good synergistic effect for providing excellent electrochemical performance,including good pore size distribution and small electron tranfer resistance in the interface between layers.3.A novel Ni foam-Ni3S2@Ni(OH)2-graphene sandwich structure electrode(NF-NN-G)with high areal mass loading(8.33 mg cm-2)has been developed by sulfide and hydrolyze reactions.The conductivity of Ni3S2 and Ni(OH)2 both improved.The upper layer of Ni(OH)2,covered with a thin graphene film,is transformed in situ from the surface of the lower layer of Ni3S2,while the Ni3S2 grown on Ni foam substrate mainly acts as a rough support bridging the Ni(OH)2 and Ni foam.The graphene stabilize Ni(OH)2 and the electrochemical properties were effectively enhanced.4.A multi-levels 3D hierarchical Zn S/Zn O/Ni9S8/Ni(OH)2 was successfully fabricated through a facile one-step hydrothermal process.A new mechanism that used Zn S as a catalyst-like material was presented here to sustainable produce Zn O to construct auxiliary structure.When Zn S hydrolysized to Zn O,the by-product H2 S can reacts with excess Zn2+ in solution and reproduced Zn S,the mechenism can promiss the structure extending to large 3D space sequentially.In addition,good electrochemical activity of Ni9S8 and Ni(OH)2 works in a good synergistic effect with the structure stability of the templates and thus provides excellent electrochemical performance.The strategy presented here for constructing multi-levels 3D structure is facile and effective,and could be expended as a general method. |
