The influence of a thermal treatment of Si/reduced graphene oxide nano-hybrid in a nitrogen atmosphere on its chemical composition and electrochemical activity

In this work, the transformation of silicon during the thermal treatment of a Si/reduced graphene oxide (rGO) nano-hybrid in a nitrogen flow over a temperature range of 800-1100 °C was investigated. A gradual decrease in the elemental Si content in the Si/rGO nano-hybrid was reflected by the decay of the electrochemical capacity of a Li-ion cell when the nano-hybrid was used as an anodic material. The heat-treated Si/rGO samples were characterized using X-ray diffraction to identify the crystalline phases. X-ray photoelectron spectroscopy was applied to determine the amorphous products. The formation of silicon oxides was observed at 800 °C. Silicon nitrides and oxynitrides were formed at 1100 °C via reaction with gaseous nitrogen. Nitrogen atoms were also incorporated into the rGO structure as pyridinic and pyrrolic groups. A very small amount of silicon carbide was detected. The high degree of oxidation in the elemental silicon was explained by its reaction with rGO-derived oxygen.