Preparation Of Organic Electrode Materials For Dual-ion Batteries And Study Of Their Electrode Reaction Mechanis

Due to unique energy storage method and structure,the dual-ion battery can choose organic electrode materials with low cost,easy synthesis and high chemical stability,combined with pure ionic liquid electrolytes with high thermal stability and electrochemical stability as needed.Therefore,the dual-ion battery can effectively alleviate the precious metal resource scarcity,while serving as an excellent energy conversion intermediary.However,organic electrode materials cannot be neglected due to the characteristic of low intrinsic conductivity.The purpose of this work is to construct a metal-free dual-ion battery with simple structure,excellent performance and green environment by using pure ionic liquid as electrolyte and organic polymer and natural graphite as electrode active materials,and to explore the mechanism of electrodes and ions in detail.Details are as follows:(1)Study of electrochemical performance of polyimide anode materials.An organic dual-ion battery based on polyimide anode(PI),natural graphite cathode(NG),and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid electrolyte(EMIm TFSI)was constructed first.The redox characteristics of PI electrode reacting/de-reacting with EMIm~+cations were tested using three-electrode cyclic voltammetry,and the same technology were carried for full battery;Fourier transform infrared(FT-IR)and scaning electron microscopy(SEM)were used to study the cyclic performance of PI electrode,plateau curve,and the cause of capacity decay.Considering the difficulty of charge transfer due to low conductivity,we try to replace the type of conducting agent(acetylene black and graphene(GR)),the content in electrode(acetylene black concentration 20%,40%,graphene concentration 1%,5%,10%,20%),and use constant current to test the effect of several methods on the cyclability,as well as differential capacitance curves to study the platform maintenance characteristics.(2)Electrochemical properties of PI/GR composite electrode materials were investigated.Considering the PI electrode with 5%GR content was made by simple stirring,PI-GR5-DIB showed good cycling stability.SEM tests revealed that GR was not uniformly distributed in the electrode,so it showed poor rate performance.The composite PI/GR with PI particles loaded on the surface of flake GR was obtained by in-situ polymerization.The surface morphology of PI/GR was observed by SEM,and the rate,cycling,and plateau performance of PI/GR-DIB were tested by constant current test;the reaction/de-reaction of EMIm~+cations was studied by XPS and CV methods,and a redox model was established.(3)In-situ modification of polyimide anode materials in dual-ion battery system.PI electrodes,whether simply added with graphene or synthesized in-situ to obtain PI/GR composites,result in lower energy specific capacity.PI/Na Cl electrodes were produced by adding inexpensive and environmental friendly Na Cl inorganic salt through the pulping process.The electrochemical process of PI/Na Cl electrode was investigated by cyclic voltammetry;the electrode morphology and cyclic stability of PI/Na Cl-DIB were tested using SEM and constant current;the redox mechanism was studied using XPS and XRD,and the in-situ modification model of polyimide was proposed.