Study On The Preparation Of Molybdenum Disulfide-based Nanocomposite And Its Sodium Storage Performance

As a typical layered transition metal sulfide,MoS₂ is considered as an ideal anode material for sodium ion batteries due to its wide interlayer spacing?0.67 nm?.However,MoS₂ has poor conductivity and large volume expansion in the electrochemical reaction process,which limits its application in sodium ion batteries.Therefore,it is an effective way to improve the performance in sodium storage by designing and synthesizing new MoS₂-based composite materials to improve its conductivity and restrain its volume expansion.Here we synthesized several MoS₂-based composites by hydrothermal synthesis and liquid phase exfoliation-reduction method.As anode materials for sodium ion batteries,their electrochemical properties have been studied.Specific research contents are as follows:1.A composite electrode material consisting of MoS₂ nanosheets anchored on nitrogen-doped carbon microtubules?NCMT?has been designed and synthesized.And the MoS₂@NCMT composite was used as anode material for sodium-ion batteries?SIBs?.The NCMT skeleton was derived from the common melamine sponges,which was used not only as a template but also as the source of nitrogen and carbon.This smart design can effectively shorten the diffusion length of Na⁺ions,increase electric conductivity of the electrode,and provide more active sites for electrochemical reactions.When evaluated as anode for sodium-ion batteries,the MoS₂@NCMT composites exhibited a high initial coulombic efficiency?67.9%?,high rate capability(196 mA h g^-1 at 10 A g^-1and 118 mA h g^-1 at 30 A g^-1)and good cycling stability(289 mA h g^-1 after 100 cycles at80 mA g^-1).2.A unique 3D nitrogen-doped graphene microtubule?NGMT?material was prepared by using a low-cost commercial melamine sponge as a template and graphene oxide as a monomer through surface dipping assembly,freeze-drying and high-temperature sintering.Using NGMT as the template,MoS₂@Nitrogen-doped graphene microtubule?MoS₂@NGMT?electrode material was prepared by a hydrothermal process.As an anode electrode material for sodium ion battery,the MoS₂@NGMT shows good cycle stability and rate performance due to the well conductivity and the stable skeleton structure of three-dimensional nitrogen-doped graphene microtubules.After 100 cycles at 100 mA g^-1 current density,the discharge capacity of MoS₂@NGMT is 407 mAh g^-1,and at 50A g^-1 current density,the discharge capacity of the MoS₂@NGMT composite is 203 mAh g^-1.3.A one pot approach to prepare carbon coated MoS₂/RGO hybrids?Ex-MoS₂/RGO@C?is proposed,which combines in-situ exfoliation of commercial MoS₂ powder and simultaneous reduction of both graphene oxide?GO?and CO₂ using liquid sodium-potassium?NaK?alloys at room temperature.As an anode material for sodium ion battery,the Ex-MoS₂/RGO@C composites exhibit high rate capability(316mAh g^-1 at 2 A g^-1)and excellent cycling stability(415 mAh g^-1 at 0.1 A g^-1 after 150cycles).The excellent electrochemical performance should be attributed to the synergistic combination of electrical conductivity of graphene,in situ carbon coating and expanded interlayer spacing of MoS₂.