Intercalation of Graphite by Aluminum Chloride. Influence of Graphite Properties on Intercalation Rate

Abstract

Kinetics of the intercalation of several well characterized graphites by aluminum chloride in the presence of chlorine were investigated in the 500 to 660 K temperature range. Temperature was the decisive parameter determining the stage of the intercalation compound. The intercalation rate depended on temperature, on graphite properties, and on partial pressures of aluminum chloride and chlorine. Crystalline perfection and amount of prismatic edges were found to be important graphite properties determining the intercalation rate. With all graphite types, the intercalation rate was linear with time in the early part of the intercalation, i.e. to about 50% of the saturation uptake. Intraparticle aluminium concentration profiles measured by electron microprobe exhibited no significant gradient of the intercalate in the intercalated region, indicating that the intercalation process was not limited by diffusion of the intercalate into the interspaces of the graphites.

Efficient Aluminum Chloride–Natural Graphite Battery

“…This battery design assumes that the intercalating species are AlCl 4 − ions, as described in early electrochemistry reports from the late 1970s. 16,39,40 This assumption is in agreement with our 27 Al nuclear magnetic resonance (NMR) spectroscopy results presented below. The graphitic cathodes in ref 15 delivered cathodic capacities of 67 mAh g −1 at an average discharge voltage of 2.0 V. The authors of ref 15 initially stated that natural forms of graphite exhibited performances much poorer than those of both tested synthetic graphitic forms.…”

“…In particular, batteries that employ metallic Al as an anode can harness numerous advantages, such as its high natural abundance, high charge-storage capacity, and safety. − In addition, Al can be reversibly deposited and stripped in chloroaluminate ionic liquids with a high Coulombic efficiency of >99.5%, without formation of dendrites. − Batteries employing chloroaluminate ionic liquids have received a great deal of attention since a publication by the group of Dai in 2015, wherein a metallic Al anode, two synthetic forms of graphite as cathodes (CVD-grown graphitic foam and pyrolytic graphite), and an AlCl 3 :EMIMCl (1-ethyl-3-methylimidazolium chloride) ionic liquid were combined into a battery, which is schematically depicted in Figure a. This battery design assumes that the intercalating species are AlCl 4 – ions, as described in early electrochemistry reports from the late 1970s. ,, This assumption is in agreement with our 27 Al nuclear magnetic resonance (NMR) spectroscopy results presented below. The graphitic cathodes in ref delivered cathodic capacities of 67 mAh g –1 at an average discharge voltage of 2.0 V. The authors of ref initially stated that natural forms of graphite exhibited performances much poorer than those of both tested synthetic graphitic forms.…”