Research On Preparation And Sodium Storge Properties Of Tin/Tin Oxide/Multilayer Graphene Composites

Lithium-ion batteries have become the most important energy source in today’s society due to their excellent cycling performance and energy density.However,the energy consumption in people’s daily life is growing exponential growth,and the development of lithium resources is increasing,leading to the lack of lithium resources.Since the mining cost of sodium salt is much lower than that of lithium salt,sodium-ion batteries have the advantages of high energy density and low environmental pollution,which have attracted more and more attention.The theoretical sodium storage capacity of SnO₂ is 667 m Ah g^-1,which has excellent sodium storage performance.However,the conductivity of SnO₂ is poor,and the volume expansion caused by the de-insertion of sodium ions will greatly reduce its electrochemical performance.In addition,the irreversible reaction of SnO₂ will generate Snand Na₂O,consuming Na⁺in the electrolyte,resulting in low initial Coulombic efficiency.In response to the above issues,the paper adopts multi-layer graphene（MLG）obtained by mechanical peeling as the substrate,which has a large specific surface area and prepares very small SnO₂nanoparticles on its surface.SnO₂ was partially reduced to Snby high-temperature treatment to prepare a Sn/SnO₂/multilayer graphene composite material with excellent performance anode material for sodium ion batteries.Specific research contents are as follows:（1）Preparation and performance study of SnO₂/multilayer graphene composites.SnO₂/multilayer graphene composites were prepared by one-step chemical bath deposition method in mixed solution of N,N-dimethylformamide（DMF）and water using SnCl₂ as tin source,HCl as growth inhibitor.The effects of HCl and SnCl₂ additions on the morphology of SnO₂/MLG composite were studied.With XRD and SEM,the composites’phase structure and morphology were determined.Results show that the best synthesis condition is 57 mg of SnCl₂and 1 m L HCl for the composite.SnO₂ nanoparticles bind well to graphene and are uniformly and densely distributed,forming a SnO₂ film on the surface of graphene.Electrochemical test showed specific capacity of 300 m Ah g^-1 was reversibly delivered at a current density of 100m A g^-1 after 100 cycles.Moreover,specific capacity of 183.92 m Ah g^-1 was delivered at a current density of 500 m A g^-1 after 300 cycles.（2）Preparation and performance study of Sn/SnO₂/multilayer graphene composites.SnO₂/multilayer graphene composite with the best microstructure was reduced at high temperature to obtain Sn/SnO₂/multilayer graphene composite.The effects of glucose addition and calcination temperature on the microstructure of Sn/SnO₂/MLG composites were studied.With XRD,SEM and TEM,the composites’phase structure and morphology were determined.The electrochemical performance of composite as anode material of sodium-ion battery was tested.Results show that the crystallinity of SnO₂ can be improved by calcination,and part of SnO₂ can be reduced to Sn.The addition of glucose can coat the surface of nanoparticles with carbon,reduce the agglomeration of nanoparticles and improve the electrochemical performance of the composite.5%glucose and calcination temperature of 800℃can obtain good microscopic morphology and sodium storage performance.Electrochemical test showed specific capacity of 490 m Ah g^-1was reversibly delivered at a current density of 100 m A g^-1after 100 cycles.Moreover,specific capacity of 355.64 m Ah g^-1was delivered at a current density of 500 m A g^-1 after 300 cycles.This sample showed excellent reversible specific capacity and cycle stability.