Synthesis And Electrochemical Properties Of Bimetallic Oxide/grapnene Composites For Libs

With the development of electrical vehicles,the increasing demand for high-capacity,high-rate lithium-ion batteries（LIBs）becomes more and more urgent.At present,the most widely used LIBs anode material is graphite,but its theoretical capacity is low,and it has gradually failed to meet the demand for higher energy storage equipment.As a potential anode material for LIBs,tin oxide（SnO₂）possesses a high theoretical capacity of 1494 mAh/g as well as the advantages of no pollution,low cost and abundant resource,and thus has good application prospects.However,the poor conductivity and large volume effect of SnO₂ severely limit its electrochemical performance as an anode for LIBs,resulting in poor cycling stability.In order to solve these issues,the bimetal oxide/graphene composites were prepared,and the synergistic effect between the two metal oxides was used to suppress the volume effect during charge and discharge process,improving the electrochemical performance.In addition,the addition of graphene futher inhibits the volume effect of bimetal oxidation,improving the conductivity and lithium storage performance.The specific research contents in this paper are as follows:1.The FeO_x-SnO₂/graphene composites were prepared by hydrothermal method.At the same time,the FeO_x-SnO₂/graphene composites were doped by nitrogen and fluorine during hydrothermal process,and the electrochemical properties of composites with different metal oxide-graphene ratios were investigated to find the optimum parameters.The experimental results indicates that,when the mass fraction of FeO_x-SnO₂ in the composite is 75.77 wt%,the FeO_x-SnO₂/graphene composite shows the best electrochemical performance.After 100 charging and discharging cycles at a current density of 0.1 A/g,the specific capacity of the FeO_x-Sno2/graphene composite can still be maintained as high as 1275 mAh/g.The improved performance of the composite material could be attributed to the synergistic effect of the two metal oxides,which improves the disadvantage of the single metal oxide.With the addition of graphene,the agglomeration of the metal oxide nanoparticles is futher prevented,and the specific surface area and electrical conductivity of the composite were also improved.2.The fluorine and nitrogen-doped CoO_x-SnO₂/graphene composites were prepared by hydrothermal method,and the content of CoO_x-SnO₂ was changed for comparison.The experimental results show that CoO_x-SnO₂/rG shows the best electrochemical performance when CoO_x-SnO₂ content is 70.62 wt%in the composite.At the 65th cycle at a current density of 0.1 A/g,the discharge specific capacity of CoO_x-SnO₂/graphene was 1253 mAh/g.3.The FeOOH-SnO₂/graphene composites were prepared by hydrothermal method in a low temperature,and the ratio of FeOOH to SnO₂ was changed to compare their electrochemical properties.The results show that the FeOOH-SnO₂/rG is the best when the ratio of FeOOH/SnO₂ is 0.75:1.After 80 cycles at the current density of 0.1 A/g,FeOOH-SnO₂/rG still delivers a high discharge capacity of up to 1209 mAh/g.The superior electrochemical performance can be ascribed to combination of the special tunnel structure of FeOOH with Sn02 to form a novel framework,which promotes the transportation of lithium ions.In addition,the synergy between FeOOH-SnO₂ and graphene also increases the structural stability,thus improving the specific surface area and lithium storage properties of the material.