The Preparation Of Nanostructured Si Materials And Application For Lithium-ion Batteries

Exploring electrode materials with high performance is critical for fabricating the next generation lithium ion battery with larger capacity, higher power density and longer cycle life. Silicon materials are expected to be the cathode electrode material of the next generation lithium ion battery and have become a research focus due to their high theoretical capacity which is10times than that of carbon, abundance in the earth’s crust, non-toxic property, etc. However, there exists large problems with silicon materials about its volume expansion in lithium and delithiation process, how to solve the fast decay of the battery capacity caused by serious volume expansion is a big challenge in the current research.This thesis aim to obtain a high performance Si electrode. The wet chemical methods was used to synthesize nanostructured SiO2, which acted as precursor and the template in the fabrication of silicon nanotubes and nano-porous structure.On one hand, SiO2nanotubes was fabricated by the electrospinning method, then Si nanotubes was fabricated by Magnesium thermal reduction along with subsequent pickling impurity removing. The influence of the parameters such as the liquid rate, applied voltage, receiving distance on the electrospinning process was researched, and finally it was confirmed that carbon coated Si nanotube can be fabricated in a controlled way by adjusting the above parameters.On the other hand, using SiO2nanoparticles as precursor and template, porous silicon material was fabricated by magnesium thermal reduction. Compared with conventional fabrication based on corrosion of monocrystalline Si wafer, this method is inexpensive and can realize controlled fabrication of porous Si. By studying the electrochemical properties of the fabricated porous Si based lithium-ion battery cathode materials, it is found that the porous Si materials have an initial discharge capacity of1245mAh/g, a charging capacity of more than963mAh/g, an initial coulombic efficiency of77.3%, and a good cycling stability.