Preparation Of Fe-based Electrode Materials And Their Electrochemical Performance For Lithium Ion Batteries

In recent years,lithium ion battery had become the most potential for development and the most advanced secondary battery.Since it has a large capacity storage,good cycle stability,safe pollution-free advantages,it is widely used in mobile phones,computers,mobile power supply and other portable tools.Lithium ion battery anode materials have a variety of options,in now adays some transition metal oxides are used as anode materials.For example,the Fe₃O₄ has many advantages,such as large specific capacity big,good cycle stability,high safety,environment friendly,etc.However the pure Fe₃O₄ electronic conductivity is not high in the charge and discharge process,because a molecule correspond to a number of lithium ion during the transmission,cause the volume change more and more bigger,it also lead to material pulverization and falls off,and generated SEI（solid electrolyte interface film）so that make the irreversible capacity loss.These disadvantages are also cause bad cycle performance and rate performance of Fe₃O₄ cathode material.So people through a variety of ways to improve the electrochemical performance of Fe₃O₄ cathode material.It is also necessary for lithium ion battery that explore the anode materials.In recent years,the poly anionic compounds has attracted many attentions of the researchers because of its special three-dimensional structure.And this kind of structure will bring the anode material many advantages.In the process of charging and discharging cycle,the migration and embedded off of lithium ions will not change the material structure,and it can effectively storage lithium ion so that make the energy density increases.And the same with the structure of LiFePO₄ due to widely exists in the nature,the price cheap,environmentally friendly and other characteristics,have attracted more and more researchers begin to study LiFe PO₄ anode material.Carbon-coated magnetite（Fe₃O₄/C）nanocomposites with hierarchical structure have been subjected to extensive research due to their relatively large specific surface area,extra free voids,and thus enhanced electrochemical performance for lithium-ion batteries（LIBs）.In this paper,Fe₃O₄/carbon nanosheets composite materials have been prepared by annealing the iron glycerinate precursor,which was synthesized by using Fe（acac）₃ as the raw material in glycerine–ethanol mixed solution.The specific discharge capacity of Fe₃O₄/C nanosheets obtained by annealing the precursor in N₂ at600°C for 3 h.The Fe₃O₄/C samples are characterized with X-ray powder diffraction,Raman,scanning electron microscopy,transmission electron microsopy,N₂ sorption isotherms,and thermogravimetric?differential scanning calorimetric techniques,and further evaluated in the role of anode materials for LIBs.The specific discharge capacity of Fe₃O₄/C nanosheets obtained retains 647 and 546 mAhg^?1 after 100 cycles at100 and 200 mAg^?1,respectively,exhibiting superior electrochemical performance to many other Fe₃O₄/C nanocomposites in previous reports.The Fe₃O₄/C nanosheets presented here not only enrich the nanomaterials community but also provide a promising candidate functioning as an anode material for effective lithium-ion storage.Carbon coated LiFePO₄ nanoparticles were synthesized by a coprecipitation method followed by anneal treatment.In the coprecipitation procedure,iron vitriol,lithium hydroxide,and phytic acid were mixed in aqueous solution to produce the precursor.The precursor was collected by filtration and dried,and then subjected to anneal treatment at 750°C for 8 h.The as-obtained LiFePO₄/C nanoparticles were characterized with XRD,Raman,FT-IR,SEM,TEM,TG/DSC and BET techniques,and tested in the role of electrochemical performance for Li-ion batteries.It is found that when cycled at 0.1 C for 100 cycles,0.5 C for 100 cycles,and 1 C for 100 cycles,the LiFePO₄/C nanoparticles exhibit exceptional reversible specific capacities of 136,116 and 99 mAhg^-1 with capacity retention close to 80%,90%,100%respectively.The electrochemical of the LiFePO₄/C sample will get better still for application in Li-ion batteries.