Research On Fabrication And Electrochemical Performance Of Lithium Tin-based Anode Materials

Tin-based anode materials(tin dioxide,tin sulfide,tin phosphide)have received extensive attention due to their high energy density and high theoretical specific capacity.They have been an extremely promising anode material for lithium-ion batteries.Because of their environmental friendliness and abundant resources,they are considered to have broad application prospects.However,it is limited by its large volume expansion coefficient,which shortens its practical application.In order to deal with this problem,two effective methods are usually adopted.One is to improve its morphology and construct a hollow spherical shell morphology to increase the specific surface area of the material,and the other is to build a layered composite structure to ease the collapse of the structure caused by the insertion of lithium ions.In this paper,firstly,solvothermal method was used to synthesize hollow spherical shell SnO2 using SiO2 as template,and four process parameters(calcination temperature,calcination time,SiO2 template size and SiO2:Na2SnO3 molar ratio)were explored morphology and electrochemical performance,respectively.The results show that when the calcination temperature was 500?,the calcination time was 2h,the size of the SiO2 template is 200 nm,and the SiO2:Na2SnO3=1:5,the SnO2 sample obtained owned the best performance.At the 0.1 C rate,the first discharge capacity of the SnO2 electrode was 1217.5 mAh/g.After 100 cycles,the discharge capacity was 507 mAh/g,which improved the defect of low SnO2 capacity retention rate.The SnO2 synthesized under the optimal conditions was the tin source,using thioacetamide(TAA)as the sulfur source,and hydrothermal synthesis of tin sulfide anode material,and the effect of calcination temperature on the synthesis material was explored.The study found that when the calcination temperature was 400?,the SnS2 nano anode material exhibited excellent electrochemical performance.On this basis,it was compounded with redox graphene(rGO)and C3N4 material synthesized from urea to prepare rGO/g-C3N4@SnS2 composite material At 0.1 C rate,the first discharge capacity of the electrode was 1133.6 mAh/g.After 400 cycles,the discharge capacity was still as high as 1048 mAh/g.At 2 C rate,the first discharge capacity was 1035.6 mAh/g,the discharge capacity remained at 852.7 mAh/g after 1000 cycles,and the Coulomb efficiency remained almost 100%,which improved the material conductivity.The SnO2 synthesized under the optimal conditions was used as the tin source,and sodium hypophosphite(NaH2PO2)was used as the phosphorus source to synthesize tin phosphide anode materials by the solid-phase method.This study found that when the reactant SnO2:NaH2PO2=1:5,Sn4P3 nano anode material was generated and exhibited excellent electrochemical performance.On this basis,it was compounded with redox graphene(rGO)and C3N4 material synthesized from urea to prepare Sn4P3@rGO/C3N4 and SnS2/Sn4P3@C3N4/rGO composite materials.Research showed that at 0.1 C rate,the first discharge capacity of SnS2/Sn4P3@C3N4/rGO electrode was 1039.2 mAh/g.After 150 cycles,the discharge capacity was still as high as 608.6 mAh/g.The capacity loss was only 26.7%,and the Coulomb efficiency was close to 100%,which greatly improved its cycle stability.