A novel elevated temperature pre-treatment for electrochemical capacity enhancement of graphene nanoflake-based anodes

Abstract

Improvements in the specific capacity of graphene nanoflake-based anodes cycled vs. Li/Li+ were investigated at two cycling temperatures of 25 and 50 °C. When cycled at 25 °C, the first cycle specific capacity of the graphene nanoflakes was 636 mA h g−1, whereas cycling at 50 °C led to a 35% increase in the specific capacity to 856 mA h g−1. High resolution SEM investigations revealed that the increased capacity of graphene cycled at 50 °C was accompanied by the formation of a uniform and continuous solid electrolyte interface (SEI). The strain generated in graphene anodes was reduced from 0.75% at 25 °C, to 0.12% at 50 °C, as determined by in situ Raman spectroscopy. This was attributed to the reduction in the extent of solvent co-intercalation at 50 °C. The results suggest that pre-cycling of Li-ion cell anodes containing graphene flakes at elevated temperatures would increase their specific capacity at the same charging/discharging current densities as that used for cycling at room temperature.