Preparation Of Fe₃O₄/C Nanocomposite And Their Electrochemical Perpormance For Lithium Ion Batteries

Fe₃O₄ is considered as a promising candidate for lithium-ion anode material due to its outstanding properties,such as high theoretical capacity?924 mAh/g?,good conductivity?2×10⁴S/m?,low cost,rich resource and environmental-friendliness.However,Fe₃O₄ based anode materials still suffer from poor cycling stability on account of the obvious volume expansion upon charge/discharge process,which severely limits its wide application.Due to the good electric conductivity and desirable cycling performance of carbon based materials,the synthesized Fe3O4/C composite is beneficial to improve the transfer rate and the structural stability for Fe₃O₄ anodes.Therefore,Fe₃O₄/C composites have essential applied value in the field of lithium-ion batteries.In order to improve the electrochemical performance of Fe3O4 anode materials,we prepared Fe3O4/C nanocomposites anodes,including carbon coated Fe3O4 nanoparticles?Fe₃O₄@C?anodes and carbon coated Fe₃O₄ nanoparticles/graphene?Fe₃O₄@C/Graphene?anodes,via hydrothermal route followed by heat treatment.The effects of synthetic process parameters and the intrant graphene on the microstructure of Fe3O4@C are studied.On these bases,different lithium-ion batteries were assembled and their electrochemical performances were investigated.The study on the synthesis and electrochemical performance for Fe₃O₄@C shows that,the increase of C/Fe mole ratio rarely affects the size of Fe₃O₄@C synthesized by hydrothermal method,but has obvious influence on the thickness rise of carbon layer.Meanwhile,increasing the concentration of reactants changes the morphology of Fe₃O₄@C from single core-shell structure to a multi-core pomegranate-like architecture.When the Fe₃O₄@C nanocomposites tested as anode materials for lithium-ion batteries,the sample synthesized by C/Fe=10,concentration of iron nitrate hydrate 0.050 mol/L delivers a reversible capacity of 806.5mAh/g after 100 cycles at a current density of 100mA/g,and it still remains at⁵70mAh/g at a current density of 1500mA/g.Fe3O4@C/Graphene nanocomposite was successfully fabricated by hydrothermal route followed by heat treatment.The as-formed Fe3O4@C nanoparticles have uniform size and good dispersion,which are uniformly distributed on the curled surface of graphene and form three-dimensional multi-level architecture.When the Fe₃O₄@C/Graphene nanocomposite tested as anode materials for lithium-ion batteries,it shows high reversible capacity,excellent cycle performance and rate capability.The reversible capacity of Fe₃O₄@C/Graphene nanocomposite can be remained 834.6mAh/g at the 120^th cycle under a current density of 100mA/g,and still remains at⁵90mAh/g under a current density of1500mA/g.