Cooperative adsorption and diffusion trapping induced by AlF3 intercalation in graphite

Abstract

Graphite's structural and electronic response to molecular intercalation is central to its performance as a carbon-based electrode material, yet the microscopic coupling between subsurface intercalation and surface adsorption remains poorly understood. We present a first-principles investigation of AlF3 adsorption and intercalation in graphite to explain the microscopic origin of a recently observed two-step self-limiting sorption mechanism. Using density functional theory (DFT-D3), we show that a single intercalated AlF3 molecule locally transforms the structure, electronic properties, and diffusion behavior of graphite through a blister-like surface deformation. Comparing pristine graphite with a graphite surface containing a subsurface intercalated molecule, coverage-dependent adsorption energetics reveal a crossover from repulsive lateral interactions to cooperative binding above the blister, driven by local curvature and intercalation-induced charge redistribution. Diffusion-barrier calculations show that the blister simultaneously acts as a kinetic trap, raising diffusion barriers and transitioning surface mobility from a quasi-barrierless to a thermally activated regime. Charge-density difference and Mulliken population analyses identify the intercalant as a stable electronic reservoir that deepens the surface potential landscape, kinetically immobilizing adsorbed species. Together, these results establish a structure-property relationship for intercalation-induced deformation in graphite, offering a quantitative framework for controlling intercalation efficiency in carbon-based energy storage and conversion systems.