Insights into the Impact of Activators on the ‘Catalytic’ Graphitization to Design Anode Materials for Lithium Ion Batteries

Hanhart, Vanessa; Frankenstein, Lars; Ramirez-Rico, Joaquin; Siozios, Vassilios; Winter, Martin; Gomez Martin, Aurora; Placke, Tobias

Abstract

In this work, we systematically investigate the ‘catalytic’ graphitization of a biomass precursor (coffee ground) using 10–60 wt. % of the activator iron (III) chloride hexahydrate in a temperature range of 1000 °C – 2400 °C. Special focus is put on the correlation of synthesis conditions, e. g., heat treatment temperature and mass fraction of iron chloride, with the electrochemical performance in carbon||Li metal cells. The structural investigations of the materials reveal a positive impact of an increasing heat treatment temperature and/or mass fraction of inserted activator on the degree of graphitization and the delithiation capacity. However, a saturation point regarding the maximum degree of graphitization at 2000 °C and reversible capacity by the ‘catalytic’ graphitization approach using iron (III) chloride has been found. A maximum degree of graphitization of ≈69 % could be reached by applying 2000 °C and 40 wt. % FeCl3 ⋅ 6H2O, resulting in a reversible capacity of 235 mAh g−1.