Study On Modification Of Ti-based Anode Materials For Lithium Ion Battery

Titanium-based anode material for lithium ion battery is a promising anode material.Li₄Ti₅O₁₂ and TiO₂ are the most studied anode materials at present.However,the lower conductivity of Ti-based materials limit its development.The modification of Ti-based anode material should be carried out to improve its electrochemical performance.This paper synthesized Li₂SiO₃/Li₄Ti₅O₁₂2 complex,different carbon doped Li₄Ti₅O₁₂2 and Li₄Ti₅O₁₂-Fe₂O₃ complexes,Si-TiO₂ and graphene loaded Si-TiO₂complexes.The structure of the materials was characterized by XRD,XPS,SEM,TEM.The electrochemical performance of the materials was investigated by Land battery test system and electrochemical workstation.And the main work is as follows:（1）Li₄Ti₅O₁₂2 and Li₂SiO₃/Li₄Ti₅O₁₂2 complex have been synthesized via a hydrothermal method.By comparing the XRD curves of Li₄Ti₅O₁₂ prepared by different titanium and lithium ratios,the ratio of Ti and Li in the preparation of Li₂SiO₃/Li₄Ti₅O₁₂ complex was 1:1.75.The characterization and electrochemical performance of Li₂SiO₃/Li₄Ti₅O₁₂ complexes which were prepared by different doping qualities of silicon shows that when 0.3 g silicon is doped,the complex exhibits excellent electrochemical performance.The initial discharge capacity is 709.5 mAh/g and the reversible capacity is 225 mAh/g after 50 cycles at the current density of 100 mA/g.It also shows that the doping structure of Li₂SiO₃ can effectively improve the electrochemical performance of the anode material of lithium ion battery.（2）LTO complexes with different carbon-doped have been prepared by ball-milling.By characterizing the structure of the complexes,the results indicate that the addition of different carbon does not completely destroy the crystal structure of materials and it prevents the agglomeration of complexes particles,which improve the electrochemical properties of LTO.Though the electrochemical performance analysis,the discharge capacity of LTO,LTO-GC,LTO-ND and LTO-GE is 100.1 mAh/g,150.4mAh/g,90.4 mAh/g and 218.3 mAh/g after 500 cycles at the current density of 175mA/g,respectively.（3）Different carbon-doped LTO-Fe₂O₃ complexes have been prepared by ball-milling.From the structural characterization of the materials,it can be observed that the doping of GC and GE can alleviate the agglomeration of LTO-Fe₂O₃.Through the electrochemical performance test,the discharge capacity of LTO-Fe₂O₃,LTO-Fe₂O₃-GC and LTO-Fe₂O₃-GE is 100.2 mAh/g,207.5 mAh/g and 238.9 mAh/g after 100 cycles at the current density of 176 mA/g,respectively.So the electrochemical properties of LTO-Fe₂O₃ complexes are excellent when doping graphene.（4）Si-TiO₂ and graphene-supported Si-TiO₂ complexes were prepared by ordinary polymerization and calcination method.And its structural characterization and electrochemical performance have been tested.The results show that when 0.3 g silicon is doped,the complex exhibits excellent electrochemical performance.The initial discharge capacity is 336.9 mAh/g and the reversible capacity is 115.8 mAh/g after 100cycles at the current density of 200 mA/g.However,due to the large volume expansion of Si in the charge and discharge process,the capacity retention rate of Si-TiO₂ complex is lower than that of TiO₂.After addition of graphene,the electrochemical properties of the material are slightly improved.When 0.5 g graphene is doped,the initial discharge capacities of complex is 356.6 mAh/g and the reversible capacity is 293.5 mAh/g after100 cycles at the current density of 200 mA/g.