Top-down design of high-performance V-based MBene anode for Li/Na-ion batteries

Two-dimensional (2D) MBenes have enormous potential in energy applications. Vanadium metal, with its versatile and tunable electronic states, can further enhance the electrochemical performance of MBenes. However, most MBenes are composed of a few atomic layers as the metal boron (MB) block, e.g., M₂B₂, which might lead to instability and poor mechanical response. Herein, we designed and predicted 2D V₄B₆ associated with different terminations (T = Cl, O, S) using a top-down method and global search for parental V₄AB₆. Among the A element candidates, the P-glued MAB phase exhibited high stability and easy synthesizability. Moreover, 2D V₄B₆ was feasibly formed and easily exfoliated owing to its weak V-P bonding. Most of the surface functionalization could improve both the mechanical and electrochemical properties of the V₄B₆ monolayer. In particular, 2D V₄B₆S₂ exhibited a high potential as an anode material for lithium-ion batteries (LIBs) with high theoretical capacity (297 mA h g^-1), low diffusion barrier (0.166 eV), and low open circuit voltage (0.136 V), outperforming a majority of MXenes and transition metal sulfide layers. This work offers a new strategy for designing desirable 2D layers from parental materials, and tuning their properties via composition and surface functionalization, which could shed light on the development of other 2D metal-ion anodes.