Electrochemical performances of graphene and MWCNT supported metallurgical grade silicon anodes

Abstract

In this study, we described the production of metallurgical grade silicon based MWCNTs and graphene reinforced composite anodes to be an alternative for solving the volume expansion problem of silicon anodes. The active materials of composite anodes were prepared via high energy ball milling methods. The first stage of production was to grind the low cost metallurgical grade silicon into micrometer particles by ring milling and high-energy ball milling methods. To get yolk-shell structure, the obtained particles were coated with carbon and etched by using hydrofluoric acid, respectively. Hummers method was used to prepare graphene oxide and the obtained graphene oxide was reduced to graphene via using hydrazine hydrate solution. We used scanning electron microscopy and X-ray diffraction to evaluate the structure and morphology of the composite anodes. The electrochemical performances of composite anodes were characterized by galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy techniques. The results indicated that the yolk-shell structured silicon/MWCNT/Graphene composite anode yielded specific discharge capacity value of 695.65mAh/g after 500 cycles at the current density of 200mA/g.