Study Of Novel Carbon-Based And Silicon-Based Anode Materials For Lithium-Ion Batteries

With the development of science and technology,the demand for secondary cell is increasing.The commonly used graphite electrodes in the market are unable to meet people's needs because of its low specific capacity(372 mAh g-1).It is found that it is an effective method to improve the electrochemical performance of the anode materials in the process of charging and discharging by improving the carbon materials and using carbon materials to modify the other anode materials.Based on the research progress of lithium ion negative electrode materials,two kinds of anode materials are explored and developed:first,using cheap and readily available biomass carbon sources and simple and feasible preparation techniques to prepare a novel carbon based anode with high capacity and good cycling performance.Second,a double core-shell nanostructure was designed and its cyclic stability and ion transport ability of silicon materials during cycling were improved by porous carbon.The results are followed:1)The common flour was used as the biomass carbon source which was annealed under 800? and treated with hydrochloric acid.Ultimately,Chloride/Nitrogen/Phosphorus doped carbon materials were obtained.It is found that graphite carbon in the material improved the electrical conductivity and electrochemical performance of the material.When used in lithium ion battery anode test,it could cycle three hundred cycles stably and keep up to 500 mAh g-1,and showed excellent rate performance.What's more,after two months standing,its capacity was reduced by only 7.2%,and it could still maintain a stable cycling performance.2)A double core-shell nanostructure(Si@C@SiO2)was designed with SiO2 as shell,and porous carbon as the middle shell to provide the volume expansion space and ion transmission channel of silicon during the cycle process.The improved cycling performance was evidenced by comparing the cycling properties of similar yolk-shell structures(Si@void@SiO2)with equal size of the intermediate shell.Based on the comparison and analysis of the experimental data,Si@C@SiO2 had more stable cycling performance and exceeded that of Si@void@SiO2 after the 276th cycle.More interestingly,the electron/ion transport ability of electrode was further improved by combination of Si@C@SiO2 with Reduced graphene oxide(RGO).Clearly,at a current density of 500 mA g-1,the reversible capacity was 753.8 mAh g-1 after 500 cycles,which was 91%of the specific capacity of the first cycle at this current density.