Synthesis,Characterization And Electrochemical Performance Research Of Tin Composites Materials

As a anode material of lithium-ion battery,the theoretical capacity of traditional graphite is only 372 mAh g^-1,which has not been able to meet people’s requirements.In recent years,development of anode materials with the high-capacity and high-cycle stability to replace traditional graphite materials has become a hot topic in lithium-ion batteries.Tin oxide has the advantages of high theoretical capacity,low lithium insertion potential and abundant resources.However,Sn O₂ suffers sever volume change during the charge and discharge process,resulting in the electrode material pulverization and poor electrochemical performance.The combination of tin oxide and other active materials can not only make use full of high theoretical capacity,but also relieve volume changes due to the synergistic effect,and improve the electrochemical performance of lithium ion battery.In this paper,the preparation process,phase and structure characterization and formation process of SnO₂ composites are discussed,meanwhile,the electrochemical performance of lithium ion battery anode material is tested.Through a series of characterization methods,the factors that affect the electrochemical performance and charge/discharge mechanism are analyzed.The following are the main research contents and results of this paper:（1）The SnO₂/Fe₂O₃ heterojunction structure composites were synthesized by a two-step hydrothermal method.The phase,morphology and size of the products were characterized by XRD,EDS,FE-SEM,HRTEM,and SAED test,to analyse the test results,we can find that SnO₂/Fe₂O₃ heterojunction structures were prepared successfully.The results showed that the prepared composite consists of SnO₂ sheets and Fe₂O₃ particles,and the Fe₂O₃ particles are attached to the surface of SnO₂,forming a stable composite material.Through the lithium chemical performance tests of single materials and the composites material,we can found that after the composite with Fe₂O₃,the lithium chemical performance of SnO₂ was significantly enhanced.At the current density of 100 mA g^-1,the discharge specific capacity still maintain at 1022 mAh g^-11 after 100 cycles.The results show that the charge/discharge capacity and the cycle performance was stability and rate performance has been improved during the good synergistic effect between the Fe₂O₃ and SnO₂ in the composites.（2）Using SnCl₂?2H₂O as the source of tin and GO as the carrier,deionized water was used as the solvent,at 180℃for 12 h were successfully prepared SnO₂/GN composites by one-step method.The composite material were combine with the SnO₂ nanoparticles and GN sheet.By the controlled the addition of graphene oxide,we obtained different content of SnO₂/GN composites.Through the analysis of the morphology and electrochemical performance of different content of compounds,the results showed that the composites with different added of graphene oxide have higher charge/discharge capacity.When the composites with 7.5 mg GO and 1 mmol SnCl₂?2H₂O added showed the best performance.At the current density of 500 mA g^-1,the initial discharge capacity was 1523 mAh g^-1,the initial coulombic efficiency was 82.5%.After 100 cycles,the reversible capacity can still be maintained at 823 mAh g^-1,with high reversible specific capacity,and stable electrochemical performance.（3）Tin（IV）chloride（SnCl₄?5H₂O）,ferric chloride（FeCl₃?6H₂O）,graphene oxide（GO）as reactants were treated with PEG-400 as solvent,and Fe₂O₃/SnO₂/GN composite materials were prepared via one-step method.In the process of solvothermal,graphene oxide has been reduced into GN.The structure and morphology of the products were characterized by XRD,EDS,FE-SEM.The characterization results showed that the Fe₂O₃ squares and SnO₂nanoparticles are anchored on the graphene sheets.The electrochemical test of the composite was carried out.Compared with Fe₂O₃/GN and SnO₂/GN composites,the interaction between the two metal oxides and the graphene sheets at the same time,makes the higher electrochemical performance and the good cycle stability at different current densities for the Fe₂O₃/SnO₂/GN composites.At a current density of 1000 mA g^-1,a high reversible specific capacity will be maintained 1038 mAh g^-11 after 300 cycles.