Preparation Of Transition Metal Compound And Carbon Composite Electrode By Electrospun And Its Energy Storage Application

Lithium-ion batteries have become the primary energy for many devices due to their superior energy density and cycle life.However,the current commercial carbon materials have low theoretical capacity and cannot meet the energy demand.Lithium-sulfur batteries have a theoretical capacity and energy density far higher than traditional lithium-ion batteries,but they are hindered by soluble lithium polysulfides（Li PSs）,shuttle effects,poor conductivity of sulfur and insoluble sulfides,which restrict their widespread application.Recently,transition metal oxides have been highly regarded for their higher theoretical capacity and good safety,but there are some problems such as poor electrical conductivity,terrible cycling and multiplicity performance.Amorphous materials can exhibit unique surface electronic states,which may improve electrocatalytic ability,while crystalline materials have long-range ordered crystal structures,showing faster electron and ion transport.Therefore,this study combines carbon-based materials with different crystallinity Fe₂O₃ as the research object,and taking their respective characteristics,we obtained high-performance negative electrode materials for lithium-ion batteries and interlayer materials for lithium-sulfur batteries.The main research content and corresponding results are as follows:1.Carbon nanofibers（CNFs）were obtained by electrospinning.Subsequently,Prussian blue were grown on carbon nanofibers（CNFs@PB）by hydrothermal growth.Using CNFs@PB as precursor,amorphous Fe₂O₃ composite carbon nanofiber materials（CNFs@C-Fe₂O₃）and crystalline Fe₂O₃ composite carbon nanofiber materials（CNFs@C-Fe₂O₃）were prepared by using Na OH treatment as well as high and low temperature annealing.2.In order to explore the performance differences between crystalline and amorphous materials in lithium-ion batteries,CNFs@A-Fe₂O₃ and CNFs@C-Fe₂O₃ are directly used as self-supporting anodes for lithium-ion batteries.The results suggest that CNFs@C-Fe₂O₃ get high mass specific capacity（based on total mass）of 372 m Ah g^-1 at current densities up to 5 A g^-1 and is capable of reaching a high reversible capacity of 771.7 m Ah g^-1 after 100 cycles at a low current density of 0.2 A g^-1,while after 500cycles at a high current density of 0.5 A g^-1,the mass specific capacity remains at 559.9m Ah g^-1 after 500 cycles at high current densities of 0.5 A g^-1.The outstanding lithium storage performance is mainly attributed to the composite of highly conductive CNFs and porous crystalline Fe₂O₃,which can alleviate the volume expansion caused by charging and discharging,provide abundant active sites,and improve the electrical conductivity of Fe₂O₃.3.In order to further investigate the performance differences between crystalline and amorphous materials in lithium-sulfur batteries,CNFs@A-Fe₂O₃ and CNFs@C-Fe₂O₃ are used as interlayer for lithium-sulfur batteries.Amorphous Fe₂O₃ has unsaturated electron coordination and abundant defect sites,which is conducive to improved electrocatalytic performance.From the visualized adsorption,it can be seen that CNFs@A-Fe₂O₃ exhibit more excellent adsorption performance of Li₂S₆,while CNFs@A-Fe₂O₃ showed higher peak current and Li₂S deposition in the symmetric cell and Li₂S deposition tests,indicating its superior electrocatalytic performance.In electrochemical tests,CNFs@A-Fe₂O₃ still had a high quality specific capacity of 632.7m Ah g^-1 at a high current density of 5 C and a capacity of 519.4 m Ah g^-1 after 500cycles at 2 C.