The Preparation Of Novel Carbon-based Porous Materials And Its Application In Electrochemical Energy Storge

The tremendous growth of portable electronic devices has promoted the increasing demand for high-power energy resources.Recently,carbon-based supercapacitors have received extensive attention because of their high power density,high charge and discharge efficiency,excellent chemical stability and low cost.All along,studies of carbon electrode materials have focused on optimizing both the pore structure and the specific surface area of materials.However,due to the fact that carbon materials tend to accumulate and the effective specific surface area is low,the storage capacity is very low.At present,the combination of electrical double layer capacitors and pseudocapacitors is a good solution.In addition,the combination of zero-dimensional hollow carbon spheres?HCSs?and one-dimensional nanotubes to obtain a composite one-dimensional structure has attracted wide attention.Therefore,in this work,we mainly studied the zero-dimensional and one-dimensional composite carbon nanomaterials,and explored the application of materials in supercapacitors and lithium-sulfur batteries.?1?Preparation of heteroatoms doped HCSs for potentialapplication in high-performance capacitanceHeteroatoms doped HCSs with micro/meso/macroporous structures are successfully prepared by one-step carbonization of polypyrrole coated polystyrene nanoparticles followed by KOH activation.The sample shows huge specific surface area(up to 935 m2 g^-1),hierarchical porous structures and high heteroatom content?³0%?.The as-prepared activated hollow carbon spheres possess a high capacitance of 535 F g^-1 at a current density of 0.2 A g^-1,and maintains 55% of the highest capacitance even at a current density of 10 A g^-1.In addition,the capacitance retention is ca.92 % after 10000 cycles.The result implies the as-prepared materials have excellent electrochemical stability.?2?Preparation of a spheres-in-tube carbon material for high-performance supercapacitorA spheres-in-tube nanostructure with hierarchical porosity is successfully engineered,by encapsulating heteroatom-doping hollow carbon spheres into one carbonaceous nanotube?HCSs@CT?.This intriguing nanoarchitecture integrates the merits of large specific surface area,good porosity and high content of heteroatoms,which synergistically facilitate the transportation and exchange of ions and electrons.Accordingly,the as-prepared HCSs@CT possess outstanding performances as electrode materials of supercapacitors,including superior capacitance to that of CTs,HCSs and their mixtures,coupled with excellent cycling life,demonstrating great potential for applications in energy storage.?3?Preparation of spheres-in-tube carbon canostructure for lithium-sulfur batteriesA number of hollow carbon spheres and a high loading amount of 72.1 wt % sulfur are both filled completely inside a large amorphous carbon tube.Owing to the presence of these electrically conductive,highly ordered and structurally robust hollow carbon spheres and a large carbon tube overlayer,sulfur material exhibits a high utilization rate and delivers a large discharge capacity of 1426 m Ah g^-1 at 0.1 C.The obtained S-H-HCSs@CT electrode demonstrates superior high-rate cycling performances,a high specific capacity of 746 m Ah g^-1 at 0.5 C can be retrained after 500 cycles.