Preparation And Electrochemical Properties Of SI-C Composites For Lithium Ion Batteries

This paper particularly reviewed the research status of lithium ion battery and summarized the actual research situation of the Si-based anode. Pyrolysising of organic materials to form amorphous carbon on the surface of Si particles was used to reduce the high irreversible capacity of the Si anode. The materials were dipped into some different salt solution to modify the surface of silicon/carbon composite. The surface morphology, composition and structure of the products were studied by XRD and SEM. Through the charge/discharge test, CV experiments and EIS analysis, the electrochemical performance of the composite were investigated.The silicon/carbon composite covered by amorphous carbon was prepared by pyrogenation method. The material whose amorphous carbon provided by resin show a performance: Its first charge capacity is 484mAh·g-1, and the first cycle efficiency is 69.99%. The material whose amorphous carbon provided by pitch give a better performance: Its first charge capacity is 728 mAh·g-1, and the first cycle efficiency is 76.5%.Adding graphite in the material can made it show a low capacity fade rateThe silicon/carbon composite modified by inorganic salt was prepared by dipping them into some different salt solution. The salt incluing NaCl, Li2CO3, Na2CO3 and KCl were chosen to prepare the solution with different concentration. The modified material show more charge capacity, better cycle stability and high first cycle efficiency of about 80%. It can be concluded from EIS that the material with good performance have low SEI impedance and low faraday impedance. The material dipped in the KCl solution has an initial charge capacity of 575.38mAh·g-1, and its charge capacity after 85 circles is 456 mAh·g-1 with a coulombic efficiency of 80%.