Rational design of MXene@VS4 heterostructures via interfacial coupling for advanced magnesium-ion batteries

Rechargeable magnesium batteries (RMBs) have garnered significant attention in energy storage applications due to their high capacity, low cost, and high safety. However, the strong polarization effect and slow kinetic de-intercalation of Mg²⁺ in the cathode limit their commercial application. This study presents a novel interface-coupled V₂CT_x@VS₄ heterostructure through a one-step hydrothermal process. In this architecture, V₂CT_x and VS₄ can mutually support their structural framework, which effectively prevents the structural collapse of V₂CT_x MXene and the aggregation of VS₄. Crucially, interfacial coupling between V₂CT_x and VS₄ induces strong V–S bonds, substantially enhancing structural stability. Benefiting from these advantages, the heterostructure exhibits high specific capacity (226 mAh g⁻¹ at 100 mA g⁻¹) and excellent long-cycle stability (89% capacity retention after 1000 cycles at 500 mA g⁻¹). Furthermore, the Mg²⁺ storage mechanism in the V₂CT_x@VS₄ composite was elucidated through a series of ex-situ characterizations. This work provides a feasible strategy for designing V₂CT_x MXene-based cathodes with high capacity and extended cyclability for RMBs.