利用镁金属化学还原法制备多孔Si/Si-O-C负极材料机理研究

以二乙烯基苯和聚硅氧烷为原料经先驱体转化法制备了Si-O-C材料，利用镁金属在惰性气氛保护下高温还原制备了多孔的Si/Si-O-C负极材料。Si/Si-O-C负极材料的首次放电与充电容量分别为547.2和450.7mAh?g-1，第二次放电与充电容量分别为487.4和422.9mAh?g-1，库伦效率分别为82.3%、86.8%，材料具有较好的循环性能。利用X射线衍射(XRD)、能谱分析(EDX)、元素分析和场发射扫描电镜(FE-SEM)分析了多孔Si/Si-O-C负极材料的组成、结构、形貌，从而研究利用镁金属化学还原法制备多孔Si/Si-O-C负极材料的机理。结果表明，镁金属在还原过程中生成MgO和Mg2SiO4等产物，经HCl洗涤后可形成多孔的Si/Si-O-C负极材料。Si/Si-O-C材料中的单质硅分布于多孔的Si-O-C相中，一定程度上可缓解Si在循环过程中产生的体积效应。利用镁金属还原Si-O-C材料制备多孔Si/Si-O-C材料是一种可行的制备方法。

The Mechanism of Porous Si/Si-O-C Anode Material Prepared by Chemical Reduction with Magnesium

Si-O-C material was prepared by a polymer-derived method using copolymer of phenyl-substituted polysiloxane and divinylbenzene as raw materials. The porous Si/Si-O-C anode material was prepared with the chemical reduction of Si-O-C material by magnesium at high temperature under argon atmosphere. The composition, structure, morphology, and formation process of porous Si/Si-O-C anode material were investigated by X-ray diffraction (XRD), energy spectrum analysis (EDX), elemental analysis and field emission scanning electron microscope (FE-SEM). The electrochemical properties of the material were characterized using electrochemical test instrument. The first discharge and charge capacity of Si/Si-O-C anode materials is 547.2 and 450.7 mAh?g-1. The second discharge and charge capacity of Si/Si-O-C anode materials is 487.4 and 422.9 mAh?g-1. The corresponding coulomb efficiency is 82.3% and86.8%, respectively. The porous Si/Si-O-C material has good cycle performance. The research results show that the magnesium will react with oxygen of Si-O-C material and turn into MgO and Mg2SiO4 during the reduction process. When washed with HCl, MgO and Mg2SiO4 react with HCl and turn into MgCl2, which can dissolve in the solution. Then, the porous Si/Si-O-C anode materials are formed. The silicon distribute in the porous Si-O-C material, which can improve the cycle performance of silicon. It can confirm that the material prepared using magnesium reduction method is a potential material for the lithium-ion battery.