Synergistic engineering of morphology regulation and sulfur vacancies in VS2 as a high-energy-density cathode for Mg-Li hybrid batteries

VS 2 has attracted extensive attention as potential host material for Mg 2+ /Li + hybrid-ion batteries (MLHBs) because of its considerable capacity and large interlayer spacing. However, the relatively weak adsorption ability and huge volume variations lead to slow reaction kinetics and poor cycle lifespan, which greatly restricts their further application in MLHBs. Herein, we have proposed a synergistic engineering of morphology regulation and sulfur vacancy for the construction of hierarchical VS 2 microflower via two pivotal procedures, which is demonstrated as a high-energy density cathode for MLHBs. Specifically, such special microflower morphology with sufficient interspace and abundant sulfur vacancies can release the inner stress to maintain structural integrity, thus leading to enhanced cycling stability. Meanwhile, the synergistic effect of flower-like structure and abundant sulfur vacancies contributes to providing sufficient redox-active sites, facilitating charge transfer, improving Li + adsorption capacity, and accelerating ion diffusion, as verified by kinetic analysis and theoretical calculations. Consequently, the hierarchical VS 2 microflower exhibits a high reversible capacity of 488.8 mAh g −1 at 100 mA g −1 , an excellent energy density of 406.6 Wh kg −1 , and an ultralong cycling stability with a capacity retention of 72.8% at 4000 mA g −1 after 2000 cycles. Besides, surface-controlled capacitive contribution analysis coupled with in-situ electrochemical impedance spectra (EIS) measurements confirm the excellent reaction kinetics. Therefore, this work presents a synergistic engineering strategy that combines morphology regulation and vacancy introduction in the fabrication of VS 2 -based cathodes for advanced MLHBs.