The Preparation Of Iron-based Sulfides Composite Material And Their Properties Research Of Lithium/Sodium Storage

Iron-base sulfides?FeS,FeS₂?,because of their advantages of high specific capacity,abundant and cheap iron sources,as well as environmental friendly,has been expected to become a candidate anode material for revisible lithium and sodium storage.However,the electrochemical properties of lithium ion and sodium ion batteries are seriously hindered due to bulk expansion effect,polysulfide by-products and poor conductivity during charging and discharging.To overcome these difficulties,this paper designed three kinds of different structure composite materials of iron-base sulfides and carbon,and tried to address the above issues.After a series of physical characterizations and performance testings,major research results are as follows:?1?Through a simple SiO₂ sphere template-assisted solid phase method,FeS nano-sheets in-situ supported on porous carbon were prepared,which shows microscopic appearance of flowers shape.This unique structure,which is formed by carbon frame and two-dimensional nanosheets,not only improve the conductivity and ionic diffusion rate of composite material but also can alleviate the problem of volume expansion,moreover,greatly enhance the active material utilization efficiency due to the increase in the contact area at the active materials and electrolytes interface.The performance test of lithium ion battery showed that the composites fabricated have:excellent rate performance,could reach 594 mAh g^-1 at the current density of 4.0 A g^-1;stable cycle performance,capacity still as high as 815.1 mAh g^-1 after 200 cycles at a current density of 1.0 A g^-1;even a better stability at the large current of 2.0A g^-1,the discharge capacity reach 996.7 mAh g^-1 after 400 cycles.?2?Combined with the advantages of doping modification,we designed a feasible scheme and nitrogen doped carbon coated FeS₂ composite materials were made.Doped nitrogen could lead to a large number of lattice defects and add more energy storage sites,which is favorable to improve capacity.Moreover,FeS₂ is limited in the carbon layer which could improve its conductivity and stability.Assessment of lithium/sodium ion battery test shows:the lithium storage capacity remains 404.2mAh g^-1 after 200 cycles at a current density of 1.0 A g^-1;when conducted constant current charge-discharge at a current density of 0.5 A g^-1,the capacity of sodium storage can also reach 472.1 mAh g^-1 after 50 cycles.?3?The intermediate product Fe₃O₄/C hollow sphere were rapidly synthesized by using the spray pyrolysis method,and then FeS₂/C hollow sphere composite material were prepared efficiently by a simple sulfidation.The hollow spherical structure of carbon coating can not only improve the conductivity but also reduce the volume expansion effect,and improve the stability of composites to some extent.Results of sodium ion battery test show:a high reversible capacity and good stability at a current density of 0.5 A g^-1,the reversible capacity remains 477.9 mAh g^-1.