Preparation And Lithium And Sodium Storage Performance Of Tin/Molybdenum Metal Sulfide Anode Materials

Anode materials play a key role in improving energy density for lithium/sodium-ion batteries.At present,commercial graphite-based anode materials greatly limits the future development of lithium/sodium-ion batteries.Tin disulfide（SnS₂）has gradually become a research focus due to its high theoretical capacity and abundant reserves.However,the inherent low conductivity and severe volume deformation of SnS₂,which lead to its poor electrochemical performance,limiting its practical application.Therefore,various material design strategies have been implemented to enhance the lithium/sodium storage capacity of the anode materials.（1）Firstly,the sheet-like SnS₂was synthesized by hydrothermal method,and the sheet-like SnS₂was coated with dopamine（PDA）to form SnS₂/PDA composite.The SnS₂/NC-rGO composites was synthesized via hydrothermal compounding with graphene oxide and then calcining in high temperature argon.The nitrogen-doped carbon layer can effectively improve the electrical conductivity,and also plays an important role in maintaining the structural stability of the material.The introduction of graphene further increases the electron/ion transfer channels,improving the ion reaction kinetics.The SnS₂/NC-r GO electrode exhibited a lithium storage capacity of 1215.8/1220.7m Ah g^-1after 200 cycles at 0.1 A g^-1.Under the same conditions,the SnS₂/NC-r GO electrode obtained a sodium storage capacity of 501.6 m Ah g^-1after 80 cycles,and the capacity retention rate is 67.02%.（2）To further improve the low electrical conductivity of SnS₂,heterostructure composites were prepared.The sheet-like SnS₂-r GO composite was synthesized via a one-step hydrothermal method.Then,the SnS₂-r GO composite was calcined to obtain a heterostructure SnS₂@SnS-r GO composites.The phase interface existing at the heterostructure contains a large number of lattice defects,which can enhance the ionic reaction kinetics,promoting the transfer of electrons and ion diffusion within the material.Thus,the lithium/sodium ion storage performance of the composites was improved.The reduced graphene oxide can effectively connect SnS₂@SnS,providing an electron transfer channel for non-contact SnS₂@SnS,thereby improving the rate capability of the electrodes.After 200 cycles at 0.1 A g^-1,the lithium storage capacity of 1339/1367 m Ah g^-1can obtained for SnS₂@SnS-r GO electrode,and Coulombic efficiency of exceeding 98%.Surprisingly,a reversible specific capacity of 685.7 m Ah g^-1can be achieved at a large current density of 5 A g^-1.The sodium storage capacity of SnS₂@SnS-r GO electrode is 608 m Ah g^-1,which achieves an excellent lithium/sodium storage capacity.（3）Bimetallic sulfide MoS₂/SnS₂/MXene composites was synthesized through three steps.First,the flower-like MoS₂/SnS₂material was prepared via two-step hydrothermal treatment.The surface modification of MoS₂nanosheets by SnS₂nanodots can prevent the mechanical strain of MoS₂during charge and discharge process.Afterward,the surface of MoS₂/SnS₂were modified from PDDA,and it have positive charge.Then,MoS₂/SnS₂were electrostatically assembled with Ti₃C₂T_x-MXene to form MoS₂/SnS₂/MXene composites.The addition of MXene enhanced the conductivity of the electrode and improved the ion transfer kinetics.The large lamellar structure not only brings abundant redox sites for lithium storage,but also enables the electrolyte to be fully contacted,thereby improving the lithium storage capacity of the electrode.The MoS₂/SnS₂/MXene electrode exhibits a high lithium storage capacity of 1260.6 m Ah g^-1at a current of 0.1 A g^-1with a Coulombic efficiency of 98.5%,which is much larger than the1053.9 m Ah g^-1obtained by the MoS₂/SnS₂electrode.The MoS₂/SnS₂/MXene electrode achieved a sodium storage capacity of 596m Ah g^-1at 0.1 A g^-1,which was higher than the 230.6 m Ah g^-1obtained by the MoS₂/SnS₂ electrode.