Iron-based Oxygen(Sulfur)Compound/Carbon Nanotube Composite Material Preparation And Its Electrochemical Performance

Energy issues are very important for national development and people's living standards.With the irreversible excessive consumption of fossil energy and the resulting environmental problems,the development and use of clean energy has caused more and more countries and Researcher's attention.At present,the development of lithium-ion batteries in the field of energy storage battery technology is relatively mature,and the applications of lithium-ion batteries can be seen in the fields of daily portable electronic equipment,new energy vehicles,and industrial energy storage.However,the large-scale use of lithium-ion batteries will gradually reduce the reserves of lithium-ion,and the global distribution of lithium resources is uneven,which will limit the development of lithium-ion batteries in the future.Sodium and lithium are both alkali metal elements,have similar physical and chemical properties,and have abundant sodium resource reserves and low development costs.They have great potential for application in future energy storage systems.It is foreseeable that the research on sodium ion batteries is one of the important directions for solving energy and environmental problems at present and in the future.To promote the commercial application of sodium-ion batteries,the key is to find electrode materials with high specific capacity,safety and stability.Among the anode materials for sodium ion batteries,transition metal oxides and sulfides,as anode materials with redox mechanism,have a higher theoretical specific capacity and first-lap coulombic efficiency,and are ideal anode materials for sodium secondary batteries.Among them,iron-based materials have attracted the attention and research of many scientific researchers due to their rich earth reserves,non-toxic and non-polluting characteristics.However,when iron-based oxides and sulfides are applied to the battery,the conductivity is poor,and the volume changes greatly during the charging and discharging process,which will cause the electrode material to be powdered and peel off from the current collector,which will lead to the battery's failure.The specific capacity and cycle stability have dropped to a large extent.This limits the application of iron-based oxides and sulfides in sodium ion batteries.In order to improve the cycle performance and rate performance of iron-based oxides and sulfides in sodium ion batteries,this article combines iron-based oxides and sulfides with carbon nanotubes with good conductivity and stable structure to prepare Fe₂O₃/carbon nanotubes,Fe1-x S/carbon nanotube composite materials.Using XRD,Raman spectrum,TG,SEM,TEM and other characterization methods to analyze the obtained samples,and then using CV,EIS and current charge and discharge test techniques to test the electrochemical performance of the samples as the negative electrode of sodium ion batteries.The main research contents and conclusions of this paper are as follows:(1)Using the flame method,three Fe₂O₃/carbon nanotube film samples with different morphologies were prepared by changing the injection rate of the catalyst,and the three samples were applied to the sodium ion battery as the negative electrode material in a self-supporting form,and The electrochemical performance test was carried out to study the relationship between the samples with different microstructures and the electrochemical performance.The results show that when the carbon nanotubes in the sample are of good quality,can be aggregated into tube bundles and can be entangled into a dense carbon nanotube network,it is beneficial to increase the sodium storage space inside the material,and the carbon nanotube network can reduce sodium storage.The stress and strain in the process can relieve the volume expansion of metal oxide particles and prevent their agglomeration,thereby improving the overall electronic and ionic conductivity of the material,making it show better electrochemical performance in sodium ion batteries.After 50 cycles of charge and discharge at a current density of 50 m A g^-1,the specific discharge capacity of 266.0 mAh g^-1 can still be maintained.(2)The iron oxide material and iron oxide/carbon nanotube composite material were prepared by hydrothermal method,and the composite material was vulcanized and modified using a fixed bed.Using the controlled variable method,the vulcanization time was changed to obtain the composition and Iron oxide/iron sulfide/carbon nanotube composite materials with different morphologies,The results show that the introduction of CNTs can effectively inhibit the agglomeration of Fe₂O₃ particles,thereby making Fe₂O₃/CNT composites have better electrochemical properties than CNT and Fe₂O₃.After charging and discharging for 100 cycles at a current density of 50 m A g^-1,The discharge specific capacity of 109.0 mAh g^-1 can still be maintained.After the Fe₂O₃/CNT sample was vulcanized,its electrochemical performance was greatly improved.After 100 cycles of charge and discharge at a current density of 50 m A g^-1,the specific discharge capacity of 348.1 mAh g^-1 can still be maintained.