Preparation And Electrochemical Properties Of Nano FeSe₂/Three-Dimensional Porous Carbon Anode Materials

Among the metal selenide materials,FeSe₂ has the advantages of large layer spacing,good electrical conductivity and high theoretical capacity,and has received wide attention in the field of sodium ion batteries.However,FeSe₂ as sodium ion battery anode material has poor FeSe₂ multiplicity in the electrochemical conversion reaction due to its slow sodium ion diffusion kinetics.Meanwhile,FeSe₂ as sodium ion anode material causes volume expansion and agglomeration phenomenon during long time charging and discharging,which greatly affects the service life of the battery.Based on this phenomenon,a carbon skeleton similar to the sponge structure can be used as the matrix of FeSe₂ to limit its expansion and agglomeration.Therefore,in this thesis,FeSe₂with high theoretical capacity is compounded with three-dimensional porous carbon（3DPC）with good electrical conductivity,and continuous large pore size honeycomb shape with microspherical FeSe₂ nanospheres uniformly inlaid inside is prepared,which gives full play to the performance advantage of high electrical conductivity of3DPC and improves the cycle stability and multiplicity of the composite material,solving the problem of FeSe₂ as a metal selenide anode material in the battery for a long time.The composite material has improved cycle stability and multiplicity,and solved the problem of volume and agglomeration caused by FeSe₂ as metal selenide anode material during the long time charging and discharging of the battery.In this,three-dimensional porous carbon（3DPC）was prepared by using Na Cl as a template and freeze-drying technology,and FeSe₂ and FeSe₂/3DPC were prepared as anode materials for sodium ion batteries by simple hydrothermal method,and FeSe₂/3DPC composites with different ratios were prepared by adjusting the FeSe₂content.The results show that the FeSe₂/3DPC composites have better electrochemical performance as sodium anode materials than FeSe₂ and 3DPC alone as sodium anode materials,with an initial discharge specific capacity of 823 m Ah·g^-1 and a capacity retention rate of 25.2%for 1000 cycles at 1 C magnification.When the FeSe₂ mass ratio is 40%（i.e.FeSe₂/3DPC-40）has the highest specific capacitance,the highest capacity retention and the best electrochemical performance with a discharge capacity of 150m Ah·g^-1 at 1 C for 1000 cycles.To further improve the cycling stability and multiplicity of FeSe₂/3DPC-40,the best ratio of FeSe₂/3DPC composites was selected,and the hydrothermal reaction temperature and hydrothermal reaction time were varied to prepare the composites by single-factor experiments.Through the characterization of the material physical and chemical properties and the testing of the electrochemical properties,the hydrothermal reaction temperature of 160℃and the hydrothermal reaction time of 16 h were optimized.This material provides a certain theoretical basis for the preparation and optimization of anode materials for sodium ion batteries.