Flame Synthesis Of Carbon-based Nanomaterials And Study On Its Electrochemical Properties

Recent years,foldable and wearable electronic devices have emerged in the electronic market,leading the development trend of the new era.The key technology of flexible electronics is the development of flexible energy storage equipment,and the development of flexible electrode materials with high capacity is the key of flexible battery technology,among which free-standing electrode as a kind of flexible electrode has gradually gained people's attention.Free-standing electrodes are mostly thin film materials with high capacity,easy assembly and high energy density,which can be directly used in batteries without the addition of conductive agent,binder and metal collector.Carbon nanotubes(CNTs)are widely used in the research of electrode materials for batteries and capacitors because of their strong mechanical and electrical properties.Carbon nanotube films are mostly prepared by filtering carbon nanotube suspension and are widely used in the process of preparing flexible electrode materials.However,the theoretical capacity of carbon material is low,which cannot meet the needs of high performance electronic energy storage equipment.Therefore,carbon nanotube film can be used as carbon matrix supporting high capacitance active materials to prepare high-performance composite electrode materials and improve the overall performance of batteries.In this paper,a thin film composite based on single-walled carbon nanotubes was synthesized by flame method.The structure and electrochemical properties of the composite were analyzed.The specific contents are as follows:(1)In the experiment of preparing single-walled carbon nanotubes(SWCNTs)by flame method,iron oxide/nitrogen doped single-walled carbon nanotubes(Fe₂O₃/N-SWCNTs)were synthesized in situ by adding nitrogen-containing precursor(urea)to the carbon source.The composite material can be directly cut and used as flexible free-steading anode material for lithium ion batteries.Electrochemical performance tests show that the composite exhibits a reversible capacity of 1022 mAh g^-1 at 50 mA g^-1 and maintains a capacity of 600 mAh g^-1 after 120 cycles at a current density of 200 mAh g^-1due to the high content of graphitic N(0.45 at%),.The lithium storage behavior of the material is mainly a surface-controlled capacitance process.Research analysis suggests that Fe₂O₃ as the active material provides a higher specific capacitance;nitrogen doping can improve the electrical conductivity of SWCNTs,accelerated the electron transfer,and show excellent rate performance;N-SWCNTs form a network structure as a carbon matrix loaded with Fe₂O₃,which can hinder the agglomeration of Fe₂O₃,relieve the stress caused by volume change in the process of charging and discharging,and make the composite material exhibit cyclic stability.(2)Compared with the lithium ion battery,the sodium ion battery has lower cost and better safety performance,so it has a broad prospect in the power grid level large energy storage equipment.In the composites,amorphous carbon has a large specific surface area,which can increases the contact area between the electrode and the electrolyte and provides abundant active sites for the reversible storage of Na⁺,SWCNTs can increase the electrical conductivity of the material to promote electron transfer,and can also be used as a supporter of amorphous carbon attachment,so that the material has excellent rate and cycling performance.Dendritic amorphous carbon/single-walled carbon nanotubes(AC/SWCNTs)composites with different proportions were synthesized in one step by flame method,and their electrochemical properties were tested.Research finding when the carbon layer spacing(0.424 nm)of AC/SWCNTs reached the maximum,the specific capacity of AC/SWCNTs remained at 220.7 mAh g^-1 at 50 mAh g^-1,and remained at 146.7 mAh g^-1after 150 cycles.The sodium storage mechanism of the composite electrode material is mainly diffusion control.In this paper,the thin-film materials with SWCNTs as the carrier were rapidly prepared by flame method,which is of great significance to improve the energy density of the battery.