NATURAL POROUS Si-C COMPOSITED WITH NITROGEN-DOPED GRAPHENE AS ANODE MATERIALS IN LITHIUM-ION BATTERIES

Abstract

Lithium-ion batteries (LIBs) have been widely used as energy storage in portable electronic devices and electric vehicles. However, graphite anode has low specific capacity and safety risks because of low operating voltage versus lithium metal which leads to battery explosion. Hence, porous siliconcarbon/nitrogen-doped graphene (Si-C/NG) composites are good candidate anode materials for the next generation LIBs. The Si-C can be derived from bamboo leaves through a calcination process and followed by magnesiothermic reduction with the various ratio of magnesium powder. To solve the low conductivity of Si-C, nitrogen-doped graphene (NG) was added by sonication to form porous Si-C/NG composites. In this report, the NG was confirmed to have graphene structure and the nitrogen content of 8.30% by Raman and XPS techniques, respectively. The phase formation of Si-C/NG was identified by XRD along with SAED patterns, which corresponded to silicon, carbon, and silicon carbide. SEM and TEM images showed the agglomeration of porous structure Si-C which was obtained together with the wrinkled paper-liked structure of NG. These composites were prepared as electrodes to study electrochemical properties including cycling stability and rate performance. Interestingly, the highest specific capacity around 500 mAhg-1 at 100 mAg-1 after 30 cycles was observed in the Si-C/NG-Mg0.3 electrode which was higher than commercial graphite.