Development And Application Of Lithium Vanadium Oxide As Anode Materials For High Performance Aqueous Lithium Ion Battery

As a new type of energy battery system,aqueous lithium ion battery will be an ideal choice for electric vehicles,energy storage power stations and other applications in the future.Lithium vanadium oxide?LiV₃O₈?is one of the most widely studied materials with the greatest development potential in recent years due to its advantages such as high energy density,simple preparation process and safety.However,there are also some disadvantages,such as:the crystal structure of the material is destroyed during charging and discharging,and the material dissolves into medium water electrolyte,which further affects the electrochemical performance of the battery.Thus,the rapid development and commercial application of lithium vanadium oxide?LiV₃O₈?material are hindered.In order to solve these problems,based on the previous research,LiV₃O₈material with hollow structure was prepared by stencil-hydrothermal synthesis method and coated with a layer of carbon layer on its surface?polystyrene is both template and carbon source?.And a series of characterization and in-depth study of the synthesized materials were carried out.The main research contents and results of this project are as follows:1)Preparation of template polystyrene?PS?.Using styrene as monomer,potassium persulfate as initiator and water as dispersing medium,PS pellets of about 100 nm were prepared by dispersion polymerization.The effects of reaction time,reaction temperature,initiator and centrifugal speed on the particle size of PS pellets were studied.It was sulfonated with sulfuric acid,and the influence of sulfonation time was studied.Finally,the structure characteristics of PS pellets before and after particle size sulfonation were characterized.2)Preparation of LiV₃O₈material with hollow spherical structure and structural characterization and electrochemical performance tests.Firstly,a layer of LiV₃O₈is coated on the surface of SPS?sulfonated modified PS?by hydrothermal method,and then the template is removed by high temperature calcination to obtain the hollow spherical LiV₃O₈material.Through electrochemical tests,it was found that the electrochemical performance of LiV₃O₈material with hollow ball structure was better than that of granular LiV₃O₈material.The first discharge capacity was 82.3 m Ah g^-1,the retention rate of capacity was 76.1%after 500 cycles,and the coulomb efficiency was77.6%.It indicates that the material has good cyclic stability.3)Preparation of LiV₃O₈@C material with hollow spherical structure and structural characterization and electrochemical performance tests.The SPS@LiV₃O₈material was carbonized in an argon atmosphere to obtain the LiV₃O₈@C composite with hollow sphere structure?in which comparative tests were conducted for different carbon contents?.Through electrochemical tests,it was found that the electrochemical performance of LiV₃O₈@C composite with hollow sphere structure was better than that of LiV₃O₈with hollow sphere structure.The first discharge capacity was 88.1 m Ah g^-1,the retention rate of battery capacity was 80.1%after 500 cycles,and the coulomb efficiency was98.3%.The results show that the material has good multiplier performance and cyclic stability.