Preparation And Sodium Storage Performance Investigation Of Tin-Based Oxide Composite Anode Materials

Tin-based materials have attracted extensive attention as promising anode materials for sodium-ion batteries（SIBs）due to their high theoretical capacity and environmental friendliness.However,their application is greatly hindered by poor sodium-ion diffusion and large volume changes during conversion and alloying processes.In this study,material optimization was implemented through reducing the particle size,compounding with conductive carbon-based materials,constructing core-shell structures,and other methods.These optimizations provide a beneficial reference for the in-depth study of high-performance tin-based oxide anode materials for SIBs.（1）In this study,ultrafine SnO₂ nanoparticles（3-5 nm）were uniform Ly grown on reduced graphene oxide（r GO）sheets through a simple one-step hydrothermal process.The nanosized SnO₂ grains could tolerate volume expansion and shorten the diffusion path of sodium ions.Moreover,r GO,as an excellent conductive matrix,endowed the composite electrode with superior electrochemical properties.The ratio of SnO₂ and r GO in the composite was also optimized.The optimized sample exhibited an initial discharge capacity of 518 m Ah g^-1 at a current density of 50 m A g^-1,and after 300 cycles at a current density of 100 m A g^-1,a discharge capacity of 504 m Ah g^-1 was achieved.In addition,after 1000 cycles at a current density of 1000 m A g^-1,a discharge capacity of 287 m Ah g^-1 was maintained.These results indicate that the SnO₂/r GO composite is a promising anode material for SIBs with excellent electrochemical performance.（2）A yolk-shell SnO₂/Co₃O₄@C composite consisting of a SnO₂/Co₃O₄（SC）core and an amorphous carbon shell was constructed.The carbon shell was decorated by Mn₃O₄ nanoparticles.It was demonstrated that this structure could further limit the volume expansion of the composite oxide SnO₂/Co₃O₄,effectively improve the conductivity of the material,and endow the composite material with excellent electrochemical performance.The optimized SnO₂/Co₃O₄@C@Mn₃O₄ provided a maximum reversible capacity of 525.6 m Ah g^-1 at a current density of 100 m A g^-1,and after 300 cycles,maintained a capacity of 491.5 m Ah g^-1,with a capacity retention rate of 93.5%.In addition,the material could withstand high current stimulation,providing a charging capacity of 435.3 m Ah g^-1 at 1000 m A g^-1.（3）Based on the research in the previous two chapters,another method for alleviating the volume expansion of the SC@C（SnO₂/Co₃O₄@C）composite was proposed.The SC@C particles were uniform Ly anchored on nitrogen-doped r GO sheets（Nr GO）,and the optimal doping ratio was explored.The sample with the optimal doping amount,SC@C/Nr GO-0.6,exhibited excellent electrochemical performance.It delivered a high reversible capacity of 532.3 m Ah g^-1 after 300 cycles at a current density of 100 m A g^-1.Moreover,it could provide a charging capacity of 350.5 m Ah g^-1 at a current density of 1000 m A g^-1.In addition,the composite r GO doped with nitrogen can effectively improve the first coulombic efficiency of the material.At a current density of 50 m A g^-1,the sample SC@C/Nr GO-0.6 has the first coulombic efficiency of 83%.