Preparation of SiC-coated silicon nanofiber/graphite composites as anode material for Li-ion batteries by CVD method

Abstract

Si material has a huge lithium storage capacity, but its huge volume change during charging and discharging makes it difficult to use. However, by nano-sizing Si material and building a coating structure, it can effectively reduce the capacity reduction caused by the expansion of Si material. In our experiment, dichlorodimethylsilane was used as the silicon source and carbon source for the deposition of silicon nanofibres and SiC-coated on a spherical graphite substrate, and then the SiC cladding was deposited without changing the temperature and silicon source, and only the C to H ratio in the atmosphere was controlled to build cladding layer. Simultaneous preparation of SiC@Si/G composites with silicon nanofibers and cladding structures by a single CVD process and single raw materials. The material has a silicon nanofiber structure and SiC coating structure. The presence of silicon is effective in providing very high capacity and the presence of the SiC layer is effective in improving the capacity retention of the composite material on the premise of increasing the Coulomb efficiency of the material. At a current density of 100 mAh g−1, the material has a reversible capacity of 647.3 mAh g−1 at first cycle. After 100 cycles, it has a 76.2 % retention rate. The electrodes can be extremely stable after cycling without significant swelling.