Synergistic engineering of heterointerfaces and sulfur vacancies in VS2/VS4 for high-performance MgLi hybrid batteries

Rechargeable Mg Li hybrid batteries (MLHBs) have gained ever-increasing attention owing to their advantages of high theoretical energy density, rich natural sources, and rapid ion intercalation kinetics. Nevertheless, the improvement of MLHBs performance is still seriously plagued by the lack of advanced cathode materials with high reversible capacity and long cycle lifespan. Herein, we have rationally designed an appealing heterostructure consisted of VS 2 microflower with expanded interlayer partially embedded into VS 4 microsphere ( E -VS 2 /VS 4 ) through a facile solvothermal reaction, serving as cathodes for MLHBs. The electrochemical results coupled with systematic kinetic investigations confirm that the synergistic effects of heterointerfaces and sulfur vacancies can facilitate charge transfer, provide rich reaction active sites, and enhance ion transport kinetics. Additionally, theoretical calculations reveal significant charge redistribution at the interface regions, which facilitates electron transfer and ion migration. Consequently, the MLHBs based on the E -VS 2 /VS 4 cathode manifest high reversible capacity (227.2 mAh g −1 at 200 mA g −1 after 70 cycles), excellent energy density (549.9 Wh kg −1 ), and ultralong cycling lifespan (123.3 mAh g −1 after 3000 cycles at 4000 mA g −1 ). Moreover, the ion storage behavior and phase evolution mechanism of E -VS 2 /VS 4 are systematically investigated by comprehensive ex-situ characterizations. This work provides an effective strategy in the rational design of cathode materials with heterointerfaces and vacancies for constructing high-performance metal-ion batteries.