Heterointerface Engineering-Induced V–C Bonds and Built-in Electric Field Boosts Mg²⁺ Storage and Diffusion Kinetics

The sluggish Mg2+ diffusion kinetics and insufficient structural stability in conventional intercalation-type materials necessitate the development of high-performance cathode materials to advance rechargeable magnesium batteries (RMBs). Herein, we propose heterointerface engineering of VS4 nanospheres in situ self-confined and anchored on a conductive Ti3C2 MXene framework (VS4@Ti3C2) to achieve fast Mg2+ diffusion kinetics. The unique design of the VS4@Ti3C2 heterointerface capitalizes on the large interchain spacing and V3+ self-doping in VS4 to facilitate Mg2+ storage, while the Ti3C2 substrate alleviates structural stress, enhances electron transport, and forms a built-in electric field at the heterointerface to accelerate ion migration. To validate the interfacial interaction mechanism, density functional theory (DFT) calculations were employed to reveal the optimized Mg2+ adsorption energy (−1.134 eV) at the heterointerface through charge redistribution and covalent V–C bond formation, accompanied by reduced diffusion barriers and mitigated structural collapse of VS4 during energy storage. Consequently, the VS4@Ti3C2 composite demonstrates a high reversible capacity of 396.5 mAh g–1 at 50 mA g–1 after activation, exceptional rate capability (121.6 mAh g–1 at 1 A g–1), and stable cycling over 1000 cycles. This study extends MXene-based cathode heterointerface engineering, establishing a versatile strategy for high-energy-density RMBs.