Two-dimensional transition metal borides (MBene), as emerging electrode materials for metal-ion batteries, exhibit diverse phase structures including MB, M2B, and M2B2. However, current research remains insufficient in exploring the M2B-phase system. This study focuses on the design of M2B-phase MBenes, pioneering the construction of two novel sulfur-functionalized materials, Zr2BS2 and Nb2BS2, while systematically elucidating their performance mechanisms as anode materials for lithium/sodium-ion batteries. Through first-principles calculations, both Zr2BS2 and Nb2BS2 demonstrate exceptional structural stability and superior electrochemical properties in sodium-ion battery applications. Specifically, they exhibit high theoretical specific capacities (624 mA h g-1 and 616 mA h g-1) and remarkably low diffusion energy barriers for Na⁺ (0.131 eV and 0.088 eV). Moreover, their low open-circuit voltages (0.38 V and 0.21 V) effectively suppress dendrite growth, achieving an optimal balance between high capacity and operational safety. This work not only establishes a theoretical framework for MBene-based anode design but also provides critical insights into the correlation between surface functionalization, structural stability, and ion transport kinetics. The findings offer valuable guidance for developing other two-dimensional materials and non-layered systems, while contributing to mechanistic understanding of charge-discharge processes in transition metal dichalcogenide TMD-based lithium/sodium-ion batteries.
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