Chalcogenated-Ti3C2X2 MXene (X = O, S, Se and Te) as a high-performance anode material for Li-ion batteries

Limited interlayer spacing and undesired surface functional group on Ti3C2 MXene surface impede the Li-ion accessibility and mobility, leading to inferior Li-storage capacity. Fine-tuning of the surface chemistry is considered as an effective approach to modulate the properties of solid surface and interface, which is extremely important for the two-dimensional (2D) electrode materials, where Li-ions residing on the surface. Herein, based on first-principle calculations, surface chalcogenation of Ti3C2 MXene, resulting in the formation of Ti3C2X2 (X = O, S, Se and Te), has been proposed to improve the electrochemical performance of Ti3C2 anode in Li-ion batteries. The results reveal that Ti3C2X2 exhibits metallic conductivity with improved mechanical strength, which renders enhanced rate performance and endures repeated lattice expansion and contraction during charge/discharge process, respectively. As compared to Ti3C2O2, Ti3C2S2 and Ti3C2Se2 render enhanced Li-ion storage and mobility with a theoretical Li storage capacity of 462.6 and 329.3 mA h/g and diffusion energy barrier of 0.25 and 0.15 eV, respectively. Moreover, chalcogenation yields expanded interlayer spacing, which improves the Li-ion accessibility in Ti3C2X2. The present study demonstrates that S- and Se- terminated Ti3C2 MXenes are promising anode materials with high capacity, low diffusion barrier and lower open circuit voltage (OCV) for next-generation Li-ion batteries.