Preparation And Electrochemical Properties Of FE3O4@C Nano-core Shell Microspheres

Anode material is one of the key factors which decide the performance and cost of lithium ion batteries.Because of its high theoretical capacity,transition metal oxides have attracted much attention.Compared with other transition metal oxides,Fe3O4 has many advantages,including high theoretical capacity,low cost,stable physical and chemical properties.Furthermore,its low pollution and high conductivity is very important.Therefore,in this paper Fe3O4 as the research object is selected to prepare Fe3O4@C yolk-shell microspheres using the novel carbon precursor and coated method.This research is to solve the problem of Fe3O4 with the poor electrochemical cycle stability induced by volume expansion.The Fe3O4@C yolk-shell microspheres,with uniform diameter and some holes on their surface,are prepared by two step hydro-thermal method,in which 1-naphthalenol is used as carbon precursor.The results show that carbon coating can significantly improve the cyclic performance of Fe3O4 electrode materials.Moreover,the two step hydro-thermal method is better than one-step one.The best preparation parameters for the two step hydro-thermal method are that the time of hydro-thermal reaction is 4h and the heat treatment temperature is 650?,The Fe3O4@C yolk shell microspheres show an optimum performance that discharge capacity keeps at 413mAh/g after 100 cycles at 100mA/g.The Fe3O4@C yolk shell microspheres are prepared by grinding,drying and carbonizing,in which Fe3O4 microspheres made by hydro-thermal method are used as core and phenolic resin is used as carbon precursor.It is found that the obtained Fe3O4@C yolk shell microspheres have uniform diameter and no agglomeration.This method of preparation is simple and easy to realize industrial production.The mass percentage of carbon coating plays an important role in improving electrochemical performance of Fe3O4@C as anode material of lithium ion battery.When the mass percentage of carbon coating is 20%,the Fe3O4@C yolk shell microspheres show an optimum performance that first discharge capacity is 984mAh/g and discharge capacity keeps at 413mAh/g after 100 cycles.The Fe3O4@C yolk shell microspheres are prepared by grinding,drying and carbonizing,in which Fe304 microspheres made by hydro-thermal method are used as core and isotropy or mesophase pitch is used as carbon precursor respectively.The purpose is to research the influence of the mass percentage of carbon coating and different kinds of pitches on the electrochemical performance of Fe3O4@C.The results show the Fe3O4@C yolk shell microspheres for both pitches show an optimum performance when the mass percentage of carbon coating is 20%.The capacity of the isotropy pitch is 437.7mAh/g and the capacity of the mesophase pitch is 396mAh/g after 100 cycles at 100mA/g.Compared to the mesophase pitch,isotropy pitch has excellent cycle stability as anode materials for lithium battery.