Preparation Of Tin-based Nanocomposites And Their Electrochemical Performance Of Lithium Storage

lithium ion battery（LIBs）have proved to be the most efficient energy storage devices,widely used in many fields such as transportation,communication,aerospace and electronics,the anode electrode is a very important part of lithium-ion battery,which has a significant impact on the overall performance of the battery based on its properties and forms.The specific capacity of existing graphite anode materials is low,which is very unfavorable to further improve the performance of lithium-ion batteries,so it is imperative to develop new anode materials.As a potential alternative material,tin-based materials have the advantages of high theoretical specific capacity and low cost,but their volume can vary greatly during lithiation and delithiumization processes,particles will also aggregate and break,causing the capacity decays rapidly,which limits the practical application of such materials.In view of this situation,this paper optimizes the modification of tin-based materials,combines tin-based materials with carbon materials by liquid phase reduction and complex chemical reduction methods,prepares Sn-SnO₂/CNT/G and Sn/G nanocomposites,and analyzes their electrochemical performance as anode materials by various characterization methods,which also provides a new method for the preparation of anode materials with higher lithium storage performance.The specific research content is as follows:（1）A nanostructured Sn-SnO₂/CNT/G composite was prepared by liquid phase reduction,the SnO₂nanocomposite phase doped with Sn provided a high active site for lithium storage,and graphene could effectively buffer the volume change of Sn-based components and prevent the pulverization of the electrode.The addition of carbon nanotubes enhances the permeability of the electrolyte in the material,which is conducive to the diffusion of lithium ions and the transport of electrons,and effectively improves the peeling phenomenon caused by the change of electrode volume during the charging and discharging process,so that the cycle performance of the electrode is significantly improved.At a current density of 100m A/g,the reversible capacity of Sn-SnO₂/CNT/G nanocomposites is still as high as 1224m Ah/g after 150 cycles.The rate performance of the composite material is very excellent,in the current density of 100m A/g,200m A/g,400m A/g,700m A/g,1A/g,its specific capacity can reach 1059m Ah/g,1013m Ah/g,927.4m Ah/g,836.7m Ah/g and 798m Ah/g;Under the high current density of 2A/g,after500 cycles,its reversible capacity can still maintain at 448.2m Ah/g,showing a good cycle and structural stability.（2）A novel Sn/graphene（Sn/G）nanocomposite was successfully prepared by complexation reduction.EDTA-2Na is used as a complexing agent and NaBH₄as a reducing agent to achieve controlled reduction of Sn²⁺.The Sn/G nanocomposites exhibits a loosely stacked structure,and ultrafine Sn nanoparticles（20-40nm）uniformly dispersing on graphene nanosheets.This specially designed morphology facilitates electrolyte penetration and efficient transport of Li-ions.After 150 cycles,the specific capacity of Sn/G nanocomposites is up to 1032m Ah/g;when the current density is 1A/g,it exhibits high rate performance of 535m Ah/g.The high conductivity and flexible network of graphene not only effectively alleviate the volume expansion of ultrafine tin nanoparticles,but also maintain the stability of the structure.In addition,Sn/G nanocomposites also have excellent structural characteristics,and good low temperature performance of 322m Ah/g is obtained at-20℃.This provides a new simple and reliable method for the synthesis of Sn/C materials,and also provides a potential candidate for low-temperature lithium storage applications.