Preparation And Performance Study Of SnO₂-MoO_3-x-based Anode Materials For Lithium-ion Batteries

With the rapid development of mobile electronic devices and electric vehicles,higher requirements have been placed on the energy density and cycle life of lithium ion batteries.Graphite is currently the most widely used anode material for lithium ion batteries in commercial applications,but the theoretical specific capacity of graphite is only 372mAh g-1,which cannot meet the development needs of high energy density lithium ion batteries.Due to its high theoretical specific capacity,abundant resources and friendly environment,metal oxide materials have become one of the most suitable lithium ion battery anode materials to replace graphite.However,the metal oxide material itself has poor conductivity,and there is a large volume effect during battery cycling.It causes the electrode material to pulverize and fall off and result in reducing the electrochemical performance of the lithium ion battery.In this study,SnO2 and MoO3-x,with two different lithium-storing mechanisms,were combined to improve the electrochemical performance.The SnO2-MoO3-x nanocomposites were prepared by hydrothermal method,and the composites were optimized and modified by adding CNTs and urea,respectively.The detailed research contents include:(1)SnO2-MoO3-x nanocomposites with different molar ratios were prepared by hydrothermal method using SnCl4-5H2O and Na2MoO4·2H2O as raw materials.The effect of the molar ratio between precursors SnCl4·5H2O to Na2MoO4·2H2O to the properties of SnO2·MoO3-x nanocomposites was discussed.By analyzing the morphology and electrochemical properties of the composites,when the molar ratio of SnCl4·5H2O to Na2MoO4·2H2O is 2:1,the properties of the obtained SnO2-MoO3-x materials are the best.(2)The SnO2-MoO3-x/CNTs nanocomposites were synthesized by one-step hydrothermal method,and the influence of the addition amount of CNTs on the properties of the composites was discussed in detail.The experimental results show that the composited CNTs have obvious improvement in structure and electrochemical properties.This is because the carbon nanotubes have good electrical conductivity and structure,improve the electrical conductivity of the electrode materials,and reduce the volume effect of metal oxide materials during battery cycling.When the addition amount of CNTs is 15wt%,the electrochemical performance of SnO2-MoO3-x/CNTs nanocomposite is the best.It has a discharge specific capacity of 532.6mAh g-1 after 100 cycles,and the coulombic efficiency is as high as 99.0%.(3)The SnO2-MoO3-x nanocomposites were modified with urea as an additive.Through the analysis of the morphology of the composites,the nanocomposites synthesized with addition of urea have better crystallinity,exhibiting nano-microsphere structure and less agglomeration on the surface of the material.Electrochemical test results show that the modified SnO2-MoO3-x nanocomposites have a significant improvement in the cycle and rate performance of lithium-ion batteries.