Intercalation of Graphite with Aluminum Fluoride: an Auger Electron Spectroscopy study

HEIDY STEFANY BETANCOURT INFANTE; ADRIANA CANDIA; SINDY RODRIGUEZ; MARIO PASSEGGI(H); SILVIA MONTORO; RICARDO VIDAL; GUSTAVO RUANO; FERNANDO BONETTO

Florianópolis, Santa Catarina

Congreso; 2024 Autumn meeting of the Brazilian Physical Society; 2024

Sociedade Brasileira de Física

Graphite is integral to numerous consumer devices, particularly in lithium-ion batteries, where it serves as the most widely used cathode material. This has led to extensive experimental and theoretical studies on compounds intercalated in graphite. Graphite’s unique physicochemical properties and highly configurable layered structure make it ideal for accommodating a variety of compounds between its flat graphene sheets.Our group recently published findings on the intercalation of aluminum fluoride (AlF3) in graphite, exploring the thermodynamic aspects from a theoretical perspective [S. J. Rodríguez et al., Phys. Chem. Chem. Phys. 23, 19579 (2021)]. We also experimentally studied the formation of ultrathin intercalates produced by UHV evaporation using techniques such as X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. These studies indicated that thermodynamics favor AlF3 intercalation over surface adsorption, with the sample's roughness limiting intercalate thickness [A. E. Candia et al., Carbon 186, 722 (2022)].To further investigate this topic, we examine the intercalation of AlF3 in graphite using Auger Electron Spectroscopy (AES) at varying evaporation rates. This method allows us to experimentally explore the kinematics and thermodynamics of the intercalation process. Our results show that the incoming AlF3 molecules are incorporated into the graphite surface in a distinct two-stage process. Initially, the molecules are fully absorbed, facilitating intercalation within the outermost graphite layers. This phase abruptly shifts to a second stage where the majority of evaporated AlF3 molecules are adsorbed onto the graphite surface. The timing of this transition, marking the onset of the second stage, is experimentally determined by varying the evaporation flux. Additionally, we conduct measurements on graphite samples of differing qualities to assess how grain sizes influence the absorption-adsorption process.