Study Of Preparation And Electrochemical Performance Of Silicon Composites As Anode Materials For Li-ion Battery

Silicon material has the highest theoretical capacity(4200mAh/g) of the materials that have been known today. Compared to the commercialized graphite material(372mAh/g), it’s more than 10 times higher. So, it has great potential as lithium-ion battery anode material. But the conductivity of silicon material is very low. And its cycling performance decline for the huge volume change in the charge-discharge process. So its commercial application is limited. Therefore, the main direction of the silicon material research is that the silicon material modification to alleviate or limit its volume effect.In this paper, using aniline as monomer, the Si/Pani composite was synthesized by stiu polymerization, the quality ratio of Si/aniline is 1:0.3,1:0.5,1:1,1:2,1:3;the Si/C composite material was prepared by stiu polymerization and pyrolysis. the quality ratio of Si/aniline is 1:1,1:2,1:3,1:4. The pyrolysis temperature is 950℃. The porous silicon material was synthesized by the disproportionation of SiO and washed with hydrofluoric acid. Using Toluene as Carbon source,the porous Si/C composite was synthesized by chemical vapor deposition.Scanning electron microscope and Fourier transform infrared spectroscopy was used analyzing the structure of the materials. The electrochemical performance of Si/Pani and Si/C composites was investigated by galvanostatic charge-discharge method. The testing condition of charge-discharge is as following: the time of charge-dicharge process is limited to 77 h, current density is 20mAh/g. When the ratio of Si/aniline is 0.5, the discharge capacity of Si/Pani composite is 1464mAh/g after cycling 19 times. When the ratio of Si/aniline is 1:3, the discharge capacity of Si/C composite is 1484mAh/g after cycling 19 times. For Si/C composite, the current density respectively is 50, 100, 200mAh/g, the reversible capacity is 1141mAh/g、930mAh/g、625 mAh/g, respectively. The results show that the ratio of carbon has influence on the electrochemical performance of Si/C composite.X-ray diffraction and N2 isorthermal adsorption-desorption analysis was used analyzing the structure of porous silicon.The electrochemical performance of porous Si and porous Si/C composites was investigated by galvanostatic charge-discharge method. The results show that: Specific surface of porous Si is 7.73m2/g, the total pore volume is 0.0144cm3/g, the average pore diameter 74.8nm. Current density is 20mAh/g, the reversible capacity of porous Si and porous Si/C composite respectively is 485 mAg/h,727mAg/h after cycling 18 times. It show that carbon is conducive to improve electrochemical performance of porous Si.