Controllable Preparation And Electrochemical Properties Of Iron Oxides Derived From Prussian Blue

With the rapid development of electric vehicles,graphite,the commercial anode material for Li-ion batteries?LIBs?,can`t meet the ever-growing demands for high energy density due to its low specific capacity.Therefore,new energy storage material is essential for lithium-ion batteries.In recent years,there has been growing research interest in deriving advanced nanomaterials with complex architectures and tailored chemical compositions from MOF based precursors for electrochemical energy storage and conversion.In this paper,we investigated Prussian blue?PB?,a MOFs energy storage material,and obtain Fe₂O₃,Fe₂O₃@C and Fe₃O₄ by controllable redox method.They were used as battery materials for lithium ion battery.Firstly,PB is synthesized by a simple coprecipitation reaction.The cubic structure of PB is attributed to the existence of PVP.The results of XRD and TEM show that the cubic PB has stable crystal structure and many channels that are suitable for intercalation and deintercalation of Li⁺,which proves its potential as electrode material of lithium ion battery.After electrochemical tests,PB owns high lithium storage capacity.The discharged capacity is 413.5mAh/g after 200 cycles at 100mA/g.Then,Fe₂O₃ with hollow cubic structure can be prepared by cubic PB.The hollow cubic porous Fe₂O₃ has unique structural advantages,such as rich mesopores,stable micro/nano and hollow structures.According to these structural advantages,the discharged capacity of the hollow cubic porous Fe₂O₃ is 1014.1mAh/g after 200 cycles at 100mA/g.The hollow cubic porous Fe₂O₃@C material can be prepared by coated with hydrothermal method.Thanks to the existence of the uniform carbon layer,the discharge capacity of the hollow cubic porous Fe₂O₃@C can reach 864mAh/g after200 cycles at 1000 mA/g.Fe₃O₄ has the advantages of large theoretical capacity,high conductivity and low cost and has potential as negative electrode material for next-generation lithium ion batteries.Hollow cage Fe₃O₄?Fe₃O₄-HMCs?can be prepared by reducing PB-derived hollow cubic porous Fe₂O₃.Fe₃O₄-HMCs own the same structure with hollow cubic porous Fe₂O₃ and superior rate performance than hollow cubic porous Fe₂O₃@C.The initial discharge capacity of Fe₃O₄-HMCs is 1235.1mAh/g.And the discharge capacity is 942.1mAh/g after 350 cycles at 1000 mA/g.