Preparation And Lithium Storage Properties Of SnS/C Composites With High Specific Energy

The coating of carbon materials is very effective in alleviating the volume change of SnS-based electrode materials and improving the cycle life of active materials.To prepare SnS-based composites with high capacity and excellent cycle life,various synthesis methods are designed by utilizing the special structure and properties of the carbon materials.Moreover,the possible lithium storage mechanism is discussed.SnS nanoparticles and SnS nanorods were prepared by uniform precipitation method and solvothermal method,respectively.The results show that SnS nanorods with one-dimensional nanorod structure exhibited better electrochemical lithium storage performance than SnS nanoparticles.The good performance of SnS nanorods can be attributed to its unique structure and morphology.SnS nanoparticles have poor performance due to the easy agglomeration of materials during charge and discharge process.Then,the surface coating of SnS was carried out by using polydopamine and copper.It was found that the coating methods could enhance the capacity and cycle life of SnS nanoparticles.SnS/carbon nanotube composites and SnS/graphene composites were successfully prepared by simple precipitation method and solvothermal method.The first coulombic efficiency of SnS/CNTs composite was 53%at 100 mA g^-1 current density,and the specific capacity of SnS/CNTs composite was 453 mAh g^-1 after 50 cycles.In addition,the composite still maintained good performance at high current.The enhanced electrochemical properties had been analyzed by transmission electron microscopy and electrochemical impedance spectroscopy,which suggested that the addition of carbon nanotube can not only reduce the volumetric variation of SnS during cycling but also promote the electron transfer.Compared with pure SnS nanoparticles,SnS/graphene composites have better electrochemical properties.The first discharge capacity of SnS/graphene composites at 100 mA g^-1 current density is 1081 mAh g^-1,the first charge capacity is 597 mAh g^-1,and the first coulomb efficiency is 55.2%.SnS/graphene composites coated with copper and polydopamine were successfully prepared by simple and economical methods.The first discharge specific capacity of SnS/graphene composite coated with copper is 1452 mAh g^-1 at 100 mA g^-1 current density,and the first charge specific capacity is 733 mAh g^-1.After 640 cycles,the specific capacity of SnS/graphene composite electrode can be maintained at 710 mAh g^-1,and good stability is maintained.To improve the electrochemical properties of SnS/graphene composites coated with polydopamine,SnS/graphene/polydopamine compostes had been successfully prepared with Sn/graphene/polydopamine as the precursor.The first discharge capacity of the composites prepared by this method is 1330 mAh g^-1 at 100 mA g^-1 current,the first charge capacity is 964mAh g^-1,and the first efficiency is achieved 67.8%.After 200 cycles,its reversible capacity can still reach 379 mAh g^-1.Low-cost and easy-obtained graphite had been introduced to fabricate SnS/graphene/graphite composites.The first charge and discharge capacities of SnS/graphene/graphite composites at 100 mA g^-1 current density were 632 mAh g^-1 and 1162mAh g^-1.The first coulomb efficiency was 54%,and the discharge capacity could be maintained at 578 mAh g^-1 after 150 cycles.