Synthesis Of Prussian Blue Composites And Derivatives Electrode Materials And Their Properties Of Sodium Storage

Into the new era,the global energy consumption continues to grow.The development and utilization of fossil fuels such as oil and natural gas brings many global problems such as global warming,environmental pollution,resource shortage and so on.It is an inevitable trend to develop renewable and clean energy.The natural renewable energy such as tidal energy,solar energy and wind energy is intermittent and unstable,so we need to store and reuse these clean energy resources.Lithium ion battery is a mature chemical energy storage way,but the lithium content is not enough and the distribution is uneven.At the same time,lithium ion batteries also have some security problems.Sodium and lithium belong to the same main group with similar chemical characteristics and abundant reserves.Therefore,room temperature sodium ion battery is considered to be a substitute for Li ion battery as large-scale grid energy storage.The performance of sodium ion batteries is mainly influenced by the electrode materials,especially the cathode materials.The cathode material is concerned with the capacity of the battery and the quality of circulation,so it is necessary to choose excellent sodium storage materials.Iron-based Prussian blue has three dimensional open frame structure and larger ion channels,and has the characteristics of high specific capacity,low cost,easy preparation,and environmental friendliness.It is a potential cathode material for sodium ion batteries.However,the low synthesis yield,poor conductivity,side reaction with the electrolyte and poor circulation stability have limited its practical application.In addition,iron based Prussian blue can be used as an iron source to react with oxygen group elements to obtain nitrogen doped carbon layer coated alloy compound nanoparticles,which can be used as anode electrode materials for sodium ion batteries.In this paper,Prussian blue and its derivatives are used as the electrode materials of sodium ion battery as the main research target.Through the optimization of the preparation method,a high-capacity iron-based Prussian blue was synthesized.After that,the sodium storage sites of the iron-based Prussian blue material and the factors affecting the performance of the iron-based Prussian blue material were further studied.Subsequently,a core-shell structure was specifically designed.Prussian blue materials are used as cathode materials for sodium ion batteries;In addition,iron and selenium by Prussian blue derivatives the first reaction elemental iron selenide nanoparticles coated with nitrogen doped carbon layer,and study the mechanism of sodium storage.The main contents of this paper are as follows:?1?This paper makes a deep study on the preparation of high performance micron-sized iron-based Prussian blue materials by the co-precipitation method with double iron.By using two iron sources of sodium ferrocyanide and ferrous sulfate,a large amount of chelating agents are used or the reaction temperature is controlled so that the rate of reaction of the double iron source is controlled,and the rate of nucleation of the iron-based Prussian blue is slowed,resulting in high capacity.Rule-cubic morphology of iron-based Prussian blue microparticles.The preparation method used has the characteristics of simplicity,controllability,safety,environmental protection and high yield.At the same time,the obtained micron-sized Prussian blue cube particles have good sodium storage electrochemical properties when used as cathode materials for sodium ion batteries,opening up new ideas for the preparation of iron-based Prussian blue.?2?We studied the mechanism of sodium storage in iron-based Prussian blue,especially Prussian blue's sodium storage sites.Combined with tests and theoretical calculations,we determined the situation of iron-based Prussian blue sodium storage sites,and explored chelating agent pairs effecting of sodium storage properties on iron-based Prussian blue materials.Subsequently,further research was conducted on further factors affecting the performance of iron-based Prussian blue cathode battery cathode materials.By setting different conditions,the iron-based Prussian blue materials of the components were formed,and the physical properties and electrochemical performance tests of these materials were performed.It was found that the adsorbed water mainly affects the specific charge-discharge capacity of the iron-based Prussian blue electrode,and its circulation is affected.Stability did not change significantly.Subsequently,through drying experiments,it was found that iron-based Prussian blue surface adsorbed water can be effectively removed under certain conditions,so that the specific storage capacity of sodium can be exerted.?3?A core-shell Prussian blue material was successfully designed and prepared for a cathodematerialforsodium-ionbatteries.Ahigh-qualitymicron-sized iron-based Prussian blue?Fe-HCF?was obtained by a dual iron source coprecipitation method.The nickel-based Prussian blue?Ni-HCF?was coated to obtain Fe-HCF@Ni-HCF microparticles.This material not only has a relatively high sodium-specific capacity for Fe-HCF,but also possesses excellent cycle stability of Ni-HCF.It is a promising cathode material for sodium-ion batteries.?4?A new selenide Fe₇Se₈ microparticle was prepared by high-temperature solid-state method and used for the first time as a negative electrode material for sodium ion batteries.In addition,X-ray photoelectron spectroscopy analysis was performed by using ex-situ X-ray powder diffraction?XRD?techniques.XPS),High Resolution Transmission Electron Microscopy?HRTEM?and other techniques reveal the mechanism of sodium storage of this material.Subsequently,we coated and modified the selenide Fe₇Se₈,using iron-based Prussian blue as the precursor and selenium element directly high-temperature solid-state reaction to obtain nitrogen-doped graphitized carbon-coated iron selenide Fe₇Se₈ nanoparticles?Fe₇Se₈@NC?as a sodium ion battery anode material.Fe₇Se₈@NC anode exhibits excellent rate performance,higher specific capacity,and excellent cycle stability.