Preparation And Electrochemical Performance Of Metal Compound/carbon Nanotube Composite

Supercapacitors have attracted a large number of researchers because of their advantages such as high power density,long cyclic life,safety and fast charge-discharge rate,but they cannot be applied on a large scale due to they cannot reach the same order of magnitude energy density as lithium-ion batteries.At present,designing high performance electrode materials is one of the strategies to improve the energy density of supercapacitors.In this paper,we mainly focus on sulfides of iron group elements metal cobalt and carbon materials.Metal sulfides hybrid materials were synthesized as the positive electrode materials of supercapacitor,and nitrogen-doped carbon nanotubes as the negative electrode materials,then supercapacitor device with high energy density was obtained.The main research contents were as follows:（1）Carbon nanotubes were directly grown on nickel mesh substrate by catalytic chemical vapor deposition（CVD）.The diameter of prepared carbon nanotubes by CVD is about 20 nm,uniform arrangement and vertical growth.The facile one-step solvothermal method was used to prepare binder-free flower-like CoS composites based on self-supported Ni@CNTs electrode.When the concentration of precursor solution was adjusted to 0.6 mmol of sulfur and cobalt sources respectively,the electrode had the best electrochemical performance.The specific capacitance of Ni@CNTs@CoS-0.6 electrode was up to 1311 F g^-1 at 1 A g^-1,and the capacitance retention was 80.5%at high current density of 10 A g^-1.（2）Using FeCl₃ as oxidant and methyl orange as soft template and structure guide agent,polypyrrole nanotubes were obtained by in situ oxidation polymerization.After high temperature carbonization and activation,nitrogen-doped porous carbon nanotubes（NCNTs）were obtained.NCNTs had abundant pores,large specific surface area,high conductivity and wettability due to nitrogen doping.The specific capacitance of NCNTs was 204.8 F g^-1 at the current density of 1 A g^-1 and the retention of capacitance was 82.0%at the current density of 10 A g^-1.（3）A hybrid supercapacitor was assembled with Ni@CNTs@CoS-0.6 as positive electrode,polypyrrole derived NCNTs as negative electrode,and 3 M KOH as electrolyte.Ni@CNTs@CoS-0.6//NCNTs/NF devices had excellent electrochemical performance.When 1 A g^-1,the specific capacitance was 81.8 F g^-1,and when the current density was 10 A g^-1,the capacitance retention was 81.8%,which had good rate capability.The device had excellent cycle lifespans,and could still maintain87.31%of the initial capacitance after 10000 cycles.The maximum energy density was 29.1 Wh kg^-1 when the power density was 800.3 W kg^-1.Even at a high power density of 8007.4 W kg^-1,the device maintained an energy density of 23.8 Wh kg^-1.