Preparation Of Carbon Nanosphere Modified Composites And Their Supercapacitance Performance Study

Supercapacitor is a new type of energy storage device,and the electrode material is the key to determine its performance.Single-walled carbon nanohorns（SWCNHs）are a new type of carbon nanostructured material,which not only has excellent electrical conductivity and typical double-layer capacitance characteristics,but also its unique conical structure makes it have many active sites,making it a highly promising supercapacitor electrode material.Transition metal oxides have high theoretical capacitance and are capable of stable redox reactions,making them popular supercapacitor electrode materials,however,their poor electrical conductivity and lower actual capacity than theoretical capacity hinder their practical application;transition metal sulfides have higher theoretical specific capacity than carbon materials and corresponding metal oxides and are rich in redox reactions,however,their poor electrical conductivity and easy agglomeration However,their poor electrical conductivity and easy agglomeration also affect their electrochemical performance.In order to exploit the advantages of carbon nanohorns as supercapacitor electrode materials and solve the problems of poor electrical conductivity and easy agglomeration of single metal oxide or single metal sulfide,binary and ternary composites of carbon nanospheres based on carbon nanohorns with metal oxides and metal sulfides were prepared in this thesis to improve the overall performance of supercapacitor electrode materials by compensating the defects of single materials through the positive synergy of different materials.performance of supercapacitor electrode materials.The main research of this thesis is as follows:（1）SWCNSs/CoFe₂O₄ composites were synthesized by polyol hydrothermal method,and both SWCNSs and CoFe₂O₄ were observed to be spherical and formed clusters by scanning electron microscopy and transmission electron microscopy;their phases,atomic valence states and elemental compositions were investigated by X-ray diffraction and X-ray photoelectron spectroscopy.The electrochemical properties of SWCNSs/CoFe₂O₄composites were studied in a three-electrode system using an electrochemical workstation.The specific capacity of SWCNSs/CoFe₂O₄ composites was 155.19 F/g at a current density of 1 A/g in a 6 M KOH electrolyte,and the specific capacitance retention was 77.4%after1000 cycles.（2）The SWCNSs/CoFe₂O₄/CuS ternary composites were synthesized by polyol hydrothermal method,and the SWCNSs/CoFe₂O₄ composites were observed by scanning electron microscopy and transmission electron microscopy microscopy attached to thin lamellar CuS;the physical phase,elemental composition and valence state of the materials were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy;the electrochemical properties of the tested The results showed that the specific capacitance of SWCNSs/CoFe₂O₄/CuS ternary composites was improved compared with that of single SWCNSs,and the specific capacitance was 211.1 F/g at a current density of 1 A/g,and the specific capacitance retention rate was 82.0%after 1000 cycles.（3）The SWCNSs/Mn Co₂S₄ composites were synthesized by a two-step hydrothermal method,and the SWCNSs were observed to be attached to the sheet Mn Co₂S₄ surface by scanning electron microscopy and transmission electron microscopy,which were characterized and analyzed by X-ray diffraction and X-ray photoelectron spectroscopy to study the material phases,elemental composition and atomic valence states of the materials.The electrochemical properties of the SWCNSs/Mn Co₂S₄ composites were tested,and the material was found to have a large specific capacitance of 382 F/g at a current density of 1A/g,and the specific capacitance retention rate was 89.3%after 1000 cycles.In summary,three carbon nanohorn-based composites,SWCNSs/CoFe₂O₄,SWCNSs/CoFe₂O₄/CuS and SWCNSs/Mn Co₂S₄,were successfully prepared in this thesis by polyol hydrothermal and two-step hydrothermal methods,respectively.SWCNSs not only improved the electrical conductivity of metal oxides and metal sulfides,but also suppressed to a certain extent the particle-like stacking of CoFe₂O₄,layered CuS and Mn Co₂S₄,which makes the ion transport and charge storage of the composites more efficient,thus increasing the specific capacitance of the composites.This thesis provides a new idea for the preparation of new supercapacitor electrode materials.