Long-range dipole–dipole interactions governing alkali-metal adsorption and clustering on graphitic surfaces

Adsorption of alkali-metal atoms on graphitic surfaces plays a fundamental role in electrochemical energy storage, particularly in carbon-based anodes such as hard carbon. Using first-principles calculations, we systematically investigate alkali-metal adsorption on graphite as a function of surface coverage and demonstrate that the adsorption energetics are governed by long-range dipole–dipole interactions between neighboring atoms. In the context of hard carbon, alkali-metal clustering on graphitic surfaces constitutes a critical initial step in the filling of micro- and nanopores. We reveal pronounced differences in the energetics and growth mechanisms of Li, Na, and K clusters and show that structural defects strongly modulate clustering and stability by providing preferential adsorption sites that alter aggregation behavior. Importantly, neglecting these long-range dipole–dipole interactions, and thus the associated surface-coverage dependence, leads to a systematic overestimation of adsorption energies and an incomplete description of alkali-metal storage in carbon-based anodes. Overall, this work provides a unified physical description of coverage-dependent, long-range dipole–dipole interactions, revealing the atomic-scale mechanisms governing adsorption energetics and high-concentration clustering in graphitic carbon, along with their implications for alkali-metal storage in carbon-based anodes.