Preparation And Lithium Storage Properties Of Carbon Composite Tin Selenide And Tin Sulfide Materials

Tin selenide（SnSe）and tin sulfide（Sn S）have the advantages of high theoretical specific capacity and environmental friendliness,and are regarded as one of the candidates for next-generation lithium-ion battery anode materials.However,tin selenide and tin sulfide have problems such as poor electrical conductivity and drastic volume changes during charging and discharging,which limit their practical applications.In view of the shortcomings of tin selenide and tin sulfide,this paper improves the lithium storage performance of tin selenide and tin sulfide by combining with conductive carbon material matrix,reducing particle size,and constructing multi-component compounds with other elements.The research of this paper is as follows:（1）SnSe nanoparticles were uniformly embedded in nitrogen-doped network carbon material（N-RC）by template method and heat treatment method to obtain SnSe/N-RC composite material.By adjusting the molar amount of tin source added,SnSe/N-RC composites with different loadings of SnSe nanoparticles were prepared.The SnSe/N-RC electrode with SnSe content of 44.7%was cycled for 500 cycles at a high current density of 2.0A/g,and the reversible specific capacity remained above 800 m Ah/g,showing good cycling stability.The main reasons for the excellent cycling stability and high capacity of the electrode are:the smaller size of SnSe nanoparticles shortens the diffusion distance of lithium ions,accelerates the surface electrochemical reaction,enhances the pseudocapacitive behavior and alleviates the effect of volume change;N-RC provides a conductive and stable structure,abundant pore structure and nitrogen-doped defects provide a large number of active sites,and enhance the ion/electron transport capability of the electrode;the interaction between SnSe nanoparticles and N-RC The tight binding avoids the direct contact of SnSe particles with the electrolyte,and also inhibits the spontaneous agglomeration of SnSe nanoparticles.（2）Using template method and heat treatment method,Sn and Cu bimetallic selenides were uniformly embedded in nitrogen-doped mesh carbon to obtain Cu₂Se₄Sn/SnSe/N-RC composite（CSS/SS/C）.CSS/SS/C composites with different two-component ratios were prepared by adjusting the molar ratio of tin source and copper source while keeping the total ion concentration unchanged.The CSS/SS/C electrode exhibits excellent rate capability,exhibiting a specific capacity of 880.9 m Ah/g at a current density of 3.0 A/g.The synergistic effect of multi-component selenides is the reason for the excellent rate performance of CSS/SS/C electrodes.Defects generated at the interface between components can not only provide additional lithium storage sites;they also build a built-in electric field,which can Enhance the rate of lithium ion diffusion and reduce the internal resistance of the battery.However,the conversion reaction to generate Cu element will lead to aggravated polarization phenomenon,and the overly complex reaction potential also increases the side reactions,and the cycle performance of the material is not improved.（3）Sn S nanosheets and Zn S nanoparticles were grown on expanded graphite（EG）by chemical oxidation and solvothermal methods,and Sn S/Zn S/EG composites（SS/ZS/EG）were prepared.The content of the two components is adjusted by adjusting the amount of tin source and zinc source added during solvothermal.When the SS/ZS/EG electrode with Sn S and Zn S loadings of 28.8%and 24.6%was cycled for 500 cycles at a current density of 1.0 A/g,the capacity kept increasing,and the specific capacity increased to 950.8 m Ah at the 500th cycle./g,showing good cycle performance.The reasons for the excellent lithium storage performance of this electrode are:the surface and interlayer structure of EG provides a large area for growing Sn S/Zn S nanoparticles,and EG has a stable structure and good conductivity,which can improve the cycle performance and rate of the electrode.performance;the overall morphology of Sn S/Zn S particles is lamellar,which can be perfectly combined with the interlayer structure of expanded graphite,which can shorten the lithium ion/electron transport path;the synergistic effect between Sn S and Zn S can further enhance the lithium storage performance of the electrode.This paper contains 46 figures,5 tables,and 105 references...