| Along with the development of economy,supercapacitor is gradually used as major energy devices in terms of fast charge/discharge,high-power density,and cycling stability.However,the lower specific capacitance and energy density have become chief factors to limit the development of supercapacitor.The performance of supercapacitor is mainly determined by the properties and structure of materials.The choice of electrode materials and reasonable structure designing will favor the highperformance supercapacitor.In this work,the hollow carbon micro-tubes were obtained by high-temperature pyrolysis of biomass,which was used as a precursor.And the airactivation and KOH-activation were introduced to prepare the porous carbons with higher surface area,respectively.Subsequently,the pseudocapacitor materials with high electronic conductivity were chosen to combine with the carbon,and designed nanocomposite with specific structure,thus to improve the whole electrochemical performance of supercapacitor.The details are described as followings:(1)The three-dimension(3D),interconnected and tubular bio-carbon were presented using the biomass Juncus effusus(JCE)via high-temperature pyrolysis.On this basis,the air-activation and KOH-activation were used to obtain the porous active carbons with higher surface area,respectively.Subsequently,the prepared active carbons were used as electrodes and assembled with symmetric supercapacitor.The experimental results demonstrated that the active carbon by air-activation could maintain the original structure to a great extent and realize to the improvement for the double electric layer properties.(2)The above-mentioned bio-carbon micro-tubes were used as a carbon substrate for loading the Ni Co2S4.The C/Ni Co2S4 composites with different structure were obtained via two-step hydrothermal method based on the Kirkendall effect.Here,the reaction time in the second hydrothermal process was changed to control and synthesize the composite with hollow tubular-on-tubular structure.The structure and components of the electrode were characterized in detail and the results showed that Ni,Co,S were uniformly distributed around the carbon tube and Ni Co2S4 grass-like nanotubes irregularly deposited internally and externally on the carbon microtube.The BET was measured and found that the hollow tubular-on-tubular structure exhibited higher surface area and rich porous distribution.To explore the electrochemical performance of supercapacitor,the hollow tubular-on-tubular composite and active carbon were used as positive and negative electrode,respectively.The assembled device indicated that the composite presented fast reaction kinetic.Benefit from the advantage of structure,the device composed of hollow tubular-in-tubular C/Ni Co2S4 could exert higher specific capacitance,excellent rate performance and considerable cycling stability.The study provides a valuable idea for the design of specific structure and the preparation of highperformance electrode materials.(3)The above-mentioned porous bio-carbon micro-tubes were used as a carbon substrate for loading the Ni-Co-compounds.A series of C/Nix Co1-x S1.097(0?x<1)composites were obtained by adjusting the molar ratios of Ni/Co via hydrothermal and thermal sulfuration processes.Related phase characterizations showed that C/Ni0.6Co0.4S1.097 exhibited stable nanowire structure and higher crystallinity when the value of x is 0.6.C/Nix Co1-x S1.097(0?x<1)were used as electrodes in a threesystem for supercapacitor.The comparison of electrochemical characterizations illustrated that C/Ni0.6Co0.4S1.097 presented higher electrochemical performance.C/Ni0.6Co0.4S1.097//AC was assembled and the results showed that the device displayed higher specific capacitance,excellent rate performance and higher energy density.Thus the C/Ni0.6Co0.4S1.097//AC can be used as a new and promising supercapacitor device. |
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