Preparation And Study On Lithium/Sodium Storage Performance Of Fe@C Composite Materials

In recent years,due to the rise of electric vehicles and various electronic devices,the study of dynamic lithium-ion batteries with high specific capacity,high rate capability and excellent cycle stability has become a research hotspot.Duo to the shortage of lithium resources and the similar electrochemical properties of sodium ions and lithium ions,the research on sodium ion cells has also received extensive attention.Metallic compound bring new directions to the study of negative electrode materials because of their higher specific capacity and abundant sources.The experimental results show that the pure metallic compound would produce serious volume effect and poor conductivity during the process of charging and discharging,resulting in poor stability and high irreversible capacity loss.Therefore,the composite of graphite and metallic compound is expected to achieve complement of material properties and improve the electrochemical properties of electrode materials.In this paper,in order to improve the reversible specific capacity and cycling stability of the material,in-situ heteroatoms doping is introduced to provide more diffusion channels and active sites for lithium/sodium ions.The main contents of this paper are summarized as follows:?1?Novel Fe₃C nanoparticles encapsulated with nitrogen-doped graphitic shells were synthesized by floating catalytic pyrolysis.Because of the short synthetic time and controllable pyrolytic temperature,the size diameters of Fe₃C core nanoparticles were ranged from 5 to 15 nmand average thickness of N-doped graphitic shells was¹.2 nm,leading to their high electrochemical performance.?2?Fe₂O₃ nanoparticles encapsulated with N-doped porous graphitic shells?Fe₂O₃@PWSs?were successfully prepared through a facile approach as anodes for SIBs.In such approach,owing to the short synthetic time,⁷ nm precursor?Fe₃C@N-doped graphitic shells core-shell nanoparticles?were prepared by floating catalytic pyrolysis,leading to in situ doped N atoms were well distributed.By partially removing homogeneous N-doped structure,lots of nanopores were created on the shell of the precursor,which made Fe₃C cores efficiently oxidized without violently destroying graphitic shells.Small size of Fe₂O₃nanoparticles?average size of 5 nm?and higher porosity of carbon shells could offer more diffusion pathway which facilitate the transportation of Na⁺/Li⁺and electrolyte leading to significantly improved electrochemical activity toward Na⁺/Li⁺storage.