Controlled Synthesis And Electrochemical Properties Research Of MoSe₂-C Anode Materials For Sodium-ion Batteries

With the constantly growing demand for high energy and power density energy storage devices,sodium ion batteries have received tremendous attention as an alternative to Li-ion batteries due to the abundant reserves and low price of sodium sources.However,the development of anode materials for sodium ion batteries（SIBs）is still confronted with many serious problems,such as low conductivity,large volume expansions,poor dynamics,low rate performance,unsatisfied cycling life and inferior capacity.Recently,2D layered transition metal dichalcogenides（TMDs）have attracted considerable attention in the fields of energy and environmental applications.Particularly,MoSe₂ is considered as a promising materials for SIBs due to its larger interlayer spacing（0.64nm）and higher electrical conductivity.This study intends to employ hydrothermal reaction method,using hollow carbon spheres as a reactor to prepare MoSe₂-C composite materials and study its electrochemical performance as anode materials for sodium ion batteries.Initially,SiO₂@SiO₂/RF nanostructure materials are fabricated by sol-gel method in one step.Subsequently,calcination of the product under N₂ at 700°C leads to the formation of SiO₂@SiO₂/C with an uniform size.The SiO₂@SiO₂/C samples were eroded with sodium hydroxide solution to study the effect of different etching time on the formation of hollow carbon nanospheres.Study found that hollow carbon nanospheres can be obtained after 2 eroding hours.Using it as a reactor combined with hydrothermal method to synthesis Few-layer MoSe₂ nanosheets with expanded（002）planes confined in hollow carbon nanospheres.The materials have ultra-long cycling life and excellent rate capabilities at high current density.The discharge capacities are502 and 471 mAh g^-1 after 1000 cycles at 1 A g^-1 and 3 A g^-1,respectively.When cycled at current densities as high as 10 A g^-1,a capacity retention of 382 mAh g^-1 can be achieved.H-Fe₃O₄@PDA material derived from H-Fe₃O₄ template are fabricated through coating technology of PDA.The material was calcined in a mixed atmosphere of hydrogen（20%）and argon（80%）at 600°C to obtain a N-doped core-shell structure Fe@YSC material.The Fe@YSC samples were eroded with hydrochloric acid solution to obtain hollow multi-layer mesoporous carbon spheres with an uniform size.Using it as a reactor to synthesis Few-layer MoSe₂ nanosheets with expanded（002）planes,which is confined in hollow carbon spheres,assembled to similar Yolk-Shell Frame MoSe₂-C material.When evaluated as anode for SIBs,the MoSe₂-C materials show ultralong cycling life.Its discharge capacity remains 378.3 mAh g^-1 over 1000cycles at 3 A g^-1.The Coulombic efficiencies reach more than 98.3%except the first one.In addition,it also exhibits outstanding rate capability.The expanded（002）planes,2D few-layer MoSe₂ nanosheets,N-doped,C-encapsulated similar yolk-shell frame are responsible for the superior electrochemical performance of the above materials.