Preparation And Electrochemical Properities Of Si/C Composite Materials

Lithium-ion battery is an important energy storage equipment,the development of high energy density,stable performance of the electrode material has become the direction of the battery development.At present,silicon material has become the focus of research on anode materials for lithium ion batteries,because of its advantages of maximum theoretical capacity and abundant reserves.However,the silicon electrode material will produce a huge volume expansion effect during the lithium alloying-dealloying process,resulting in the electrode pulverization and the rapid decline in battery capacity.In view of the above problems,it is an effective solution to compound carbon material with nano silicon particles.In this paper,carbon nanotubes and graphene were used as carbon sources,and mesoporous silica was used as silicon source,the Si/C composites were prepared by hydrothermal method and confirmed by means of transmission electron microscopy(TEM),scanning electron microscope(SEM)and X-ray diffraction(XRD).The preparations and the electrochemical properties of Si/C composite materials have been studied.The main results are as follows:(1)The Si/C composite materials were prepared with CNT as the C source,and the influence of magnesium thermal reduction temperature on material structure and electrochemical properties was studied.Results suggest that the reaction temperature at 650 ℃,the materials show the best electrochemical performance,the discharge capacity is 645.6 mAh/g after 100 cycles at a current density of 100 mA/g.(2)The Si/C composite materials were prepared with RGO as the C source,and the influence of magnesium thermal reduction temperature on material structure and electrochemical properties was studied.Results show that the reaction temperature at 650 ℃,the materials have the best structure,the conductivity and cycling stability of electrode materials have been improved.(3)The Si/C composite materials were prepared with CNT and RGO as the C source.The results show that graphene,carbon nanotubes,and silica balls can be combined well at 650 ℃ reaction temperature,wherein the silica ball is attached to the surface of the carbon tube,and the silica ball and the graphene exist in the middle of the graphene sheet.the discharge capacity is 707.5 mAh/g after 100 cycles at a current density of 100 mA/g,showing the best performance with good rate capability.