  The electrolyte intercalation mechanism facilitates the insertion/extraction
of charge into the electrode material in rechargeable batteries. Aluminum
fluoride (AlF$_{3}$) has been used as an electrolyte in rechargeable aluminum
batteries with graphite electrodes, demonstrating improved reversibility of
battery charging and discharging processes; however, the intercalation
mechanism of this neutral molecule in graphite is so far unknown. In this work,
we combine scanning tunneling microscopy (STM) in ultra-high vacuum conditions,
calculations based on density functional theory, and large-scale molecular
dynamics simulations to reveal the mechanism of AlF$_{3}$ intercalation in
highly oriented pyrolytic graphite (HOPG). We report the formation of AlF$_{3}$
molecules clusters between graphite layers, their self-assembly by graphene
buckling-mediated interactions, and explain the origin and distribution of
superficial {\it blisters} in the material. Our findings have implications for
understanding the relationship between the mobility and clustering of molecules
and the expansion of the anode material. This, in turn, paves the way for
future enhancements in the performance of energy storage systems.
