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

The sluggish Mg 2+ 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 VS 4 nanospheres in situ self-confined and anchored on a conductive Ti 3 C 2 MXene framework (VS 4 @Ti 3 C 2 ) to achieve fast Mg 2+ diffusion kinetics. The unique design of the VS 4 @Ti 3 C 2 heterointerface capitalizes on the large interchain spacing and V 3+ self-doping in VS 4 to facilitate Mg 2+ storage, while the Ti 3 C 2 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 Mg 2+ 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 VS 4 during energy storage. Consequently, the VS 4 @Ti 3 C 2 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.