Study On The Simple Preparation And Capacitive Performance Of Micronanostructured Carbon And Its Composite Electrode Materials

In recent years,ascribing to the explosive growth of new energy vehicles and mobile electronic devices,the portable electrochemical energy storage devices,such as lithium ion batteries and supercapacitors,have been put forward with increasing high requirements.As the core of supercapacitor,electrode material decides the performance and price of supercapacitor.Thus,it is of great scientific and practical value to develop electrode material with low cost and excellent performance for high performance commercial supercapacitor.In this paper,using benzene and its homolores as raw materials,the multi-wall carbon nanotubes and carbon micron spheres with excellent performance were rapidly and simply prepared by high-temperature self-pressure method.Meanwhile,the metal catalysts used in the preparation process were comprehensively utilized to further prepare multi-wall carbon nanotubes/metal sulfide nanocomposite.The morphology,structure and phase of the prepared electrode materials were systematically characterized,and the electrochemical properties of the prepared carbon nanotubes,carbon micron spheres and carbon nanotubes/metal sulfide nanocomposite were systematically studied.?1?Using benzene as the carbon source and ferrocene as the catalyst,multi-wall carbon nanotubes?MCNTs?were prepared via high-temperature self-pressure method without the protection of inert atmosphere,and their preparation conditions were systematically optimized.The results show that when the pyrolysis temperature is800?,the ratio of catalyst and carbon source mole is 1:2,and the pyrolysis time is30min,the morphology and purity of the prepared multi-wall carbon nanotubes are the best.The electrochemical properties of the samples prepared under optimal conditions were compared with those of typical commercial carbon nanotubes.At the current density of 0.5 A g^-1,the specific capacitance of the self-made MCNTs is as high as 64F g^-1,while the specific capacitance of the typical commercial multi-wall carbon nanotubes is only 21 F g^-1,the specific capacitance of the self-made MCNTs is about three times higher than that of typical commercial multi-wall carbon nanotubes.When the current density increases from 0.5 A g^-11 to 20 A g^-1,the capacitance retention rate of the prepared MCNTs sample is as high as 95.5%.After 10,000 charge/discharge cycles,there is no significant capacitance loss?99.5%?.Compared with other commercial MCNTs,MCNTs prepared by this method has better electrochemical properties.?2?Taking benzene as the raw material,ferrocene as both the iron source and the catalyst,and sublimated sulfur as the sulfur source,a CNT@Fe₇S₈ nanocomposite was simply and quickly prepared via high-temperature self-pressure--vulcanization method by fully utilizing the iron nanoparticles generated in the process of preparing carbon nanotubes.The product was systematically compared with Fe₇S₈ nanomaterial.The results showed that most of the Fe₇S₈ nanoparticles adhered on the surface of MCNTs or was coated by the MCNTs.The CNT@Fe₇S₈ nanocomposite was applied to the supercapacitor and the specific capacitance reached 587.1 F g^-11 at the current density of 1 A g^-1.When the current density increases from 1 A g^-1to 10 A g^-1,the capacitance retention rate of the nanocomposite is about 74.5%,which is 1.32 times higher than that of the Fe₇S₈ nanomaterial?56.4%?.After 5,000 times charge/discharge cycles,the capacitance retention of the prepared CNT@Fe₇S₈nanocomposite was about 2.4 times higher than that of the Fe₇S₈ nanomaterial,which was significantly increased from 23.6%to 56.2%,indicating that the electrochemical performance of the Fe₇S₈ nanomaterial could be greatly improved by combining with the self-made MCNTs.A hybrid supercapacitor of NiS₂//CNT@Fe₇S₈ is faricated using CNT@Fe₇S₈ nanocomposite as negative electrode and NiS₂ nano materials as postive electrode,the work voltage of the hybrid supercapacitor is increased to 1.8V.Under the voltage window of 0¹.8V,the specific capacitance and energy density reached 68.9 F g^-11 and 31.0 Wh kg^-1,respectively.More than 61.7%of initial specific capacitance was maintained after 5000 charge/discharge cycles,indicating that it is a promising electrode material in the field of electrochemical energy storage.?3?Using phenol as carbon source and ferrocene as catalyst,carbon microspheres?CS?were prepared via high-temperature self-pressure method without the protection of inert atmosphere,and the preparation conditions were systematically optimized.The results show that when the pyrolysis temperature is 800?and the pyrolysis holding time is 30min,the prepared carbon microspheres exhibits optimal morphology and purity.The microspheres that prepared under optimal conditions exhibits a high specific capacitance of 161 F g^-11 at a current density of 0.5 A g^-1,more than 89.5%of specific capacitance was retaiened when the current density increased from 0.5 A g^-11 to 20 A g^-1.After 10,000 times charge/discharge cycles,the capacitance retention is up to 97.2%,showing excellent rate and cycling performance.