Regulating MXene Interlayer Chemistry: A Facile Vapor-Phase Sulfurization Strategy for Enhanced Lithium Storage

MXene-based materials are promising anodes for lithium-ion batteries due to their metallic conductivity and layered structures. However, conventional surface terminations create heterogeneous interlayer chemistry, causing uneven charge distribution, sluggish Li+ transport, and inefficient utilization of active sites. Herein, we report a vapor-phase sulfurization strategy to construct sulfur-modulated layered materials from MAX precursors. Sulfur incorporation modulates the local electronic environment, enhancing electronic coupling and Li+ migration pathways. Density functional theory calculations reveal increased electronic states near the Fermi level, reduced charge localization, and lower Li+ diffusion barriers compared with Ti3C2Tx MXene. Consequently, Li+ storage in sulfur-modulated S–Ti3C2 involves both interlayer insertion and sulfur-related Faradaic reactions, delivering a reversible capacity of 955 mAh g–1, approximately 2.6 times that of conventional HF-etched Ti3C2Tx. This work demonstrates that vapor-phase sulfurization provides an effective route for regulating the electronic structure and charge-storage chemistry of MAX-derived layered materials.