Synthesis And Electrochemical Performance Of Anode Materials For Lithium-ion Batteries Based On Fe₂O₃

With the rapid development of global economy,the rapid consumption of fossil fuels and the increasing concern for the environment,there is an urgent need for efficient,clean and sustainable energy.Lithium ion battery has the advantages of high energy density,long life,no memory effect and environmental friendliness.The performance of lithium-ion batteries depends to a large extent on the performance of electrode materials,and many attempts have been made to develop high-performance lithium-ion battery electrode materials.For example,Fe₂O₃-based anode materials for lithium-ion batteries are considered to be very developed energy storage materials due to their high theoretical specific capacitance,low cost and non-toxicity.However,the decrease in cycle performance caused by low conductivity and volume expansion are the two main problems that hinder their further development.Therefore,in response to the above problems,this article covers,doped and quenched Fe₂O₃materials to improve the electrochemical performance of the materials.The research content is as follows:1.Using NH₄HF₂ and LiOH as raw materials,a series of Fe₂O₃materials with different amounts of LiF coating were prepared by the neutralization precipitation method.Through the cycle test,15%of the coated material was selected as the object of further research.Characterize the phase and structure of the sample through a series of physics such as SEM,TEM,BET and XPS.Since the coating effectively relieves the volume expansion of Fe₂O₃during charge and discharge,the material exhibits better electrochemical performance than uncoated Fe₂O₃under the same electrochemical performance test conditions.The research results show that LiF@Fe₂O₃material as the negative electrode of lithium-ion battery has an initial discharge specific capacity of 1209 m Ah g^-1at a current density of 1.0 A g^-1,and gradually declines to 540 m Ah g^-1during the first 80 cycles.After 200 cycles,the discharge specific capacity rebounded to about 950 m Ah g^-1and remained stable.After 500 cycles,it can reach 304 m Ah g^-1at a current density of 5.0 A g^-1.2.Through a simple solvothermal method,the F-Fe₂O₃ material was synthesized in one step.Through XRD and XPS test analysis,it is concluded that F doping causes O vacancies in Fe₂O₃materials.Compared with undoped Fe₂O₃,the electrochemical performance of F-Fe₂O₃is improved.Under 1.0 A g^-1,the initial discharge specific capacity is 1257 m Ah g^-1,and the first 30 cycles decay faster.After300 cycles,the capacity can rise up to 1032 m Ah g^-1,which is compared with the first discharge specific capacity.The rate is as high as 82%.The increase in the capacity of the F-Fe₂O₃material should be mainly attributed to the replacement of part of the O^2-by F^-,resulting in a defect with a unit negative charge,which promotes the conductivity of the F-Fe₂O₃material to be enhanced,promotes the electrode reaction kinetics,and improves Electrochemical performance.3.Through the quenching technology,the F-Fe₂O₃ material prepared in the previous chapter is prepared through a two-step experimental process to prepare the quenched F-Fe₂O₃material.Through physical analysis such as XRD,XPS,SEM,TEM and BET,it is concluded that the crystal surface of the quenched F-Fe₂O₃material shrinks,the particle size becomes smaller,and the surface of the material becomes round and smooth.In addition,after the electrochemical performance test,it is found that the electrochemical performance after cold quenching can be further improved.Under 1.0 A g^-1,the initial discharge specific capacity is 1353 m Ah g^-1.After 500 cycles,it can still provide 1008 m Ah g^-1,and the capacity retention rate is as high as 74%.At 0.1,0.2,0.5,1.0,2.0 and 5.0 A g^-1,the discharge specific capacity is 1467,1388,1208,1034,805 m Ah g^-1,533 m Ah g^-1,when the current density returns to 0.1 A g^-1,the discharge specific capacity of 1536 m Ah g^-1can be quickly reached,showing excellent electrochemical performance.This is due to the fact that the quenching technology not only increases the number of chemically active sites on the surface of the material and reduces the particle size,but also alleviates the volume effect in the electrochemical process of the F-Fe₂O₃ material.