Strain-Engineered Interfacial Chemistry: Curvature-Induced sp2–sp3 Rehybridization of Graphene for Ultrahigh Alkali Metal Storage

Abstract

Graphene-based anodes often suffer from limited storage capacity and sluggish kinetics due to the chemical inertness of the pristine basal plane. Traditional activation strategies, such heteroatom doping or defect engineering, often compromise the superior mechanical integrity of materials. Herein we propose a nondestructive surface engineering strategy by demonstrating that mechanical buckling is not merely a physical deformation but also a potent chemical activator. Using first-principles calculations, we unravel the mechanism of curvature-induced rehybridization, where compressive strain disrupts the delocalized π-electron system, forcing a local transition from sp2 to partial sp3 character. We further identify three distinct activation mechanisms driven by the interplay between strain and metal adsorption. For weak compression, the graphene sheet remains planar until metal adsorption induces a reversible buckling, representing a dynamic active site mechanism where the structure recovers planarity upon desorption. For moderate compression (e.g., 5%), metal atom adsorption triggers a transition to a corrugated state that persists after desorption due to mechanical load, yet without π–σ orbital mixing. In contrast, under higher compression (e.g., 10% or 15%), the system undergoes an irreversible transition to a stable corrugated state where curvature is locked by both compressive force and π–σ coupling. This electronic modulation creates highly polarized active sites at the convex “ridges” and concave “valleys”, significantly enhancing the interfacial binding affinity for Li, Na, and K adatoms. Unlike planar graphene, the buckled architecture facilitates a multilayer adsorption mechanism, yielding exceptional theoretical specific capacities of ∼1675.1 mA h g–1 for a Li-ion battery and ∼744.5 mA h g–1 for a Na- and K-ion battery, far surpassing the commercial graphite anode. Furthermore, we identify anisotropic ion diffusion pathways, i.e., “ridge” and “valley”, where the valley channels exhibit ultralow energy barriers (<0.05 eV), acting as superionic highways for rapid kinetics. Our findings establish a robust structure–property relationship between geometric curvature and surface reactivity, providing a theoretical blueprint for designing next-generation flexible anodes via straintronics.