Structural and electrochemical properties of fullerene-coated silicon thin film as anode materials for lithium secondary batteries

By performing a plasma evaporation technique, fullerene C60 was used as a coating material onto a silicon thin film anode for lithium secondary batteries. The effect of the plasma power (20 W, 100 W and 200 W) in the plasma coating process on the structural and electrochemical properties of the fullerene C60-coated silicon anode was then studied by means of Raman spectroscopy, Fourier transform infra red (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and charge/discharge tests. The Raman and FTIR analysis showed that the polymeric phase of fullerene C60 was formed during the deposition operation and that the fullerene monomers were polymerized to a greater extent at a high plasma power operation (200 W). Furthermore, the fullerene C60-coated silicon electrode obtained at a plasma power of 200 W exhibited excellent electrochemical performance with a specific capacity of more than 2000 mAh g−1. The stable polymeric phase of fullerene C60 was found to be the main factor enhancing the electrochemical performance of the fullerene-coated silicon anode.