Design And Synthesis Of Iron Based Sulfide Composite And The Study On Its Electrochemical Performance

Alkali metal ion batteries occupy an important academic and application position in electrochemical energy storage devices.Among them,lithium-ion battery(LIB)have been widely used in various portable electronic products due to their advantages such as high energy density and long cycle life,and they are expected to be used in flexible equipment,electric vehicles and small power stations.However,due to the low storage of lithium resources in the earth's crust,the price of lithium is expensive,which makes the high-efficiency lithium-ion batteries were limited to some extent in large-scale application to a certain extent.Both sodium and potassium,which are alkali metals,have similar chemical properties to lithium,and have more abundant reserves in the earth's crust than lithium.Therefore,low-cost sodium ion batteries(SIB)and potassium ion battery(PIB)has great potential to become the important energy storage devices in large-scale energy storage.In this paper,the working principles,research status,and electrode materials of three secondary alkali metal ion batteries are briefly introduced first.Then,three types of iron sulfide nanocomposite designed and synthesized as the anode for secondary alkali metal ion batteries are introduced in detail.The main research results are as follows:(1)A novel 3D porous architecture with a graphene nanoscrolls(GNS)/nanosheet hybrid as the framework and ultrasmall Fe1-x S/Fe3O4 hetero-nanoparticles(NPs)as the primary active matter was prepared by the technology of cold quenching,freeze drying and the subsequent roll-in treatment.The electrochemical performance of this material as LIB anode was then tested,and the results showed that the flexible electrode exhibits high reversible specific capacity(946 m Ah?g~-1 at 0.1A?g~-1)and good long-cycle stability(up to 400 Cycle,a low capacity decay rate of 0.047% per cycle),which is benefit its unique and stable 3D structure.In addition,compared with the traditional two-dimensional graphene material,its rate performance is also significantly improved(capacity retention of 40.1% at 6 A?g~~-1).(2)A hybridized 3D network material configuration which is constructed by interconnected monodispersed graphene nanosheets(MGNs)with confined Fe S2/Fe S hetero-nanoparticles(NPs)as the main active matter through a facile cold quenching-gas phase sulfidation technology.The performance of this composite material(Fe S2/Fe S NPs@MGN)as SIB anode was then tested.Benefiting from the distinctly wrinkled surface feature and rich multiscale pores in materials,which shows excellent rate performance and almost no attenuated cycling performance.Under the ultra-high current density of 20 A?g~-1,a reversible capacity of 251 m Ah?g~-1 can still be obtained,and the capacity retention is as high as 52.7%.Under the condition of 0.1 A?g~-1,it can maintain a high capacity of 513 m Ah?g~-1 after 100 discharge / charge cycles.In addition,the superior confine effect on the suppression of polysulfide shuttling and the loss of active materials is also demonstrated.(3)Explore the possibility of using expanded graphite(EG)as a low-cost carrier in alkaline metal ion batteries.A carbon-coated iron sulfide(Fe1-x S)nanoparticles anchored on the surface of S-doped EG(C@Fe1-x S/S-EG)composite is prepared by a facile two-step gas-phase reaction route.The results show that the obtained composite material exhibits excellent lithium and potassium storage performance due to the double confine of the carbon layer and EG on the Fe1-x S nanoparticles.As the anode of lithium ion battery,it exhibits considerable capacity retention and rate performance.It can maintain a capacity of 834 m Ah?g~-1 after 100 cycles,and delivers a capacity of 600 m Ah?g~-1 at a current density of 1 A?g~-1.As for potassium ion batteries,it behaves the prolonged cycle life and excellent rate performance.The capacity retention rate is 47% after 5000 cycles at the current density of 1.4 A?g~-1,and delivers a stable discharge capacity of 73 m Ah?g~-1 at the ultra-high current density of 14 A?g~-1.However,the prepared composite materials deliver a poor capacity of sodium storage.It delivers a low charge capacity of 276 m Ah?g~-1 at a current density of 100 m A?g~-1,while its cycle performance is stable.