Preparation, Modification And Electrochemical Properties Of SnO₂-MoO_3-x Composite Lithium-ion Battery Anode Materials

In recent years,the research of lithium-ion batteries was attracted more and more people's attention.Anode materials are an important part of lithium-ion batteries,and different materials have a great impact on battery performance.At present,the commercial negative electrode material mainly uses graphite material,and its theoretical capacity is only 372 mAh/g,which cannot meet the demand for large capacity batteries.Metal oxides have a high specific capacity,and the metal oxides SnO₂ and MoO₃ have received extensive attention due to their higher theoretical capacity,ease of manufacture,large quantity,low cost,and eco-friendliness.SnO₂,as a representative of metal oxides whose lithium storage mechanism is an alloy type,has a theoretical capacity of 782 mAh/g.But during the charging and discharging process,the insertion and extraction of lithium ions undergoes a large volume change up to 300%.This leads to severe chalking of the electrode,and ultimately leads to rapid capacity degradation during cycling.MoO₃ is a typical conversion anode material with a theoretical capacity of up to 1117 mAh/g.The delithiation-intercalation of SnO₂ and MoO₃ occurs in different potential ranges,and the volume change of the electrode occurs gradually,thereby alleviating the volume effect.In this paper,SnO₂/MoO_3-x nanocomposites are synthesized by hydrothermal method,and their structure and properties are optimized and modified by doping carbon nanotubes and graphene.The specific research contents are as follows:1.By controlling the molar ratio of Sn and Mo,pure SnO₂and SnO₂/MoO_3-xnanocomposites with different ratios were synthesized.The research results show that the molar ratio of Sn/Mo in Sn Cl₄·5H₂O to Na₂MoO₄·2H₂O is 2:1,the composite exhibits the best electrochemical performance.Under the current density of 200 mA/g,the first discharge specific capacity is 1566.8mAh/g,and the first coulombic efficiency is 43.03%.After 120 cycles,the specific capacity remains at 431.7 mAh/g,and the coulombic efficiency reaches 99.04%.2.The carbon nanotubes and SnO₂/MoO_3-xbinary materials with a molar ratio of Sn/Mo of 2:1 were combined to prepare SnO₂/MoO_3-x/CNTs ternary nanocomposites with different carbon nanotube contents.Research results show that 15%carbon nanotubes are composited,the composite exhibits the best electrochemical properties.Under the current density of 200 mA/g,the first discharge specific capacity is 2045.8mAh/g,and the first coulombic efficiency is 52.34%.After 140 cycles,the specific capacity remains at 591.4 mAh/g,and the coulombic efficiency reaches 99.05%.3.The graphene and SnO₂/MoO_3-xbinary materials with a molar ratio of Sn/Mo of 2:1 were combined to prepare SnO₂/MoO_3-x/graphene ternary nanocomposites with different graphene contents.The research results show that 50%graphene is composited,the composite shows the best electrochemical performance.Under the current density of 200 mA/g,the first discharge specific capacity is 1940.1 mAh/g,and the first coulombic efficiency is 52.4%.After 150 cycles,the specific capacity remains at 645.8 mAh/g,and the coulombic efficiency reaches 99.07%.