Self-healing ion blocking via adaptive surface fluorination of graphene lamellas

Safety failures in high-energy lithium-ion batteries often originate from uncontrolled interfacial transport and electrolyte decomposition at elevated voltages. Existing coatings and artificial interphases provide limited protection because they degrade under the oxidative, fluorine-rich conditions generated by LiPF₆-based electrolytes. Here, we demonstrate that hot-pressed graphene (HP-Gr) foils operate as an autonomous, self-healing chemical system, in which electrolyte decomposition products are converted in operando into a stable, self-limiting fluorinated surface layer. Rather than being detrimental, interfacial reactions trigger adaptive chemical passivation that restores and preserves interfacial function. By decoupling lamellar densification from surface chemistry, the materials design enables independent control of transport morphology and self-generated chemical protection. The resulting fluorinated skin suppresses Li⁺ penetration while preserving electronic and thermal transport, as confirmed by depth-resolved spectroscopy. This work establishes adaptive surface fluorination as a self-healing interfacial mechanism, providing a general strategy for transforming unavoidable chemical degradation into functional stabilization in multifunctional carbon materials.