Preparation Of Nanostructured Tin Oxide Composite And Optimization Of Its Energy Storage Performance

The requirement of the lithium-ion batteries with high specific capacity and long-life is getting higher with the development of society.The anode material is an important part of lithium ion battery,which can store Li+ during the stage of discharge.Tin oxides(SnO2 and Sn3O4)are considered as a promising candidate for lithium-ion batteries owing to the high theoretical specific capacity,the high abundance of Sn,low cost and environmental benignity.The main insufficient of tin oxide anode are shown as follows:(1)the mass loss of initial irreversible capacity caused by the formation of Li2O and SEI film;(2)is significantly limited by their poor cycling stability due to the large volume change during the process of lithium ion insertion and desorption.The defects of tin oxides can be improved by reconstructing specific nanostructures and compositing with carbon-based matrix.In this paper,using different tin sources as precursor and graphene or carbon nanotubes as carbon substrate,composite materials are prepared and exhibited excellent electrochemical properties.The details are showed as follows:Considering the SnC14 5H2O and NaOH as raw materials,a ternary composite of tin oxide nanorods/carbon nanotubes/graphene(Sn02/CNTs/Gr)with 3D-architectures is synthesized via one-pot hydrothermal method,and investigated as anode for lithium-ion batteries.Compared to bare SnO2 and corresponding binary composites including SnO2/CNTs and SnO2/Gr,the ternary composite shows significantly improved cycling stability and rate performance.The results show that the initial discharge specific capacity of the SnO2CNTs/Gr electrode is 1391 mAh/g and the reversible capacity is 522 mAh/g after 50 cycles at a current density of 100 mA/g,corresponding coulombic efficiency is 97%.At 1600 mA/g,the discharge specific capacity of SnO2/CNTs/Gr is as high as 120 mAh/g.When the current density is restored to 50 mA/g,the ternary composite can be restored to 582 mAh/g and stabled until 100th.The significant electrochemical performance of SnO2/CNTs/Gr nanocomposite can be attributed to the synergistic effect of SnO2 nanorods,carbon nanotubes and graphene.The Sn3O4 nano-flower is synthesized by solvothermal method with SnSO4 and sodium citrate as the raw materials,and it is modified by silane coupling agent.Afterwards,the flower-like ternary composite material of carbon nanotubes/graphene-encapsulated tin oxide(Sn3O4/CNTs/Gr)is synthesized with a simple solution method driven by the mutual electrostatic interactions.The initial specific capacity of the Sn3O4/CNTs/Gr is 1459 mAh/g and the reversible capacity is 697 mAh/g after 100 cycles at a current density of 100 mA/g.At 1600 mA/g,the reversible capacity remains 255 mAh/g,and the reversible capacity recovers to 697 mAh/g when it is restored to 50 mA/g again.The excellent electrochemical performance of Sn3O4/CNTs/Gr can be attributed to the synergistic effect among Sn3O4 nano-flower,graphene and carbon nanotubes,which increases the electrical conductivity of the composite and improves the structural stability.