A theoretical study on the intercalation and diffusion of AlF₃ in graphite: its application in rechargeable batteries

Using first-principles calculations based on density functional theory (DFT), we study the aluminum fluoride (AlF₃) intercalation in graphite as a new possibility to use this molecule in rechargeable batteries, and understand its role when used as a component of the solvent. We discuss the most stable configuration of the AlF₃ molecule in graphite for stage-2 and stage-1 and the diffusion study of the molecule, the migration pathways and the energy barriers. Our results show an average voltage of 3.18 V for stage-2 and 3.44 V for stage-1, which is excellent for anion intercalated batteries. Furthermore, low diffusion energy barriers of the AlF₃ intercalant molecules were found (the lowest diffusion energy barrier was 0.17 eV with a diffusion constant in the order of 10^-5 cm² s^-1), which could lead to fast (dis)charging of a battery based on AlF₃. The present study provides important information to understand the intercalation mechanism of AlF₃ graphite layer electrodes, thus encouraging more experimental studies of this system.