Strategy of cation/anion co-doping for potential elevating of VS4 cathode for magnesium ion batteries

VS4 is one of the most potential cathode materials candidates for magnesium ion batteries (MIBs). However, it is still challenging for suitably modifying VS4 to make it process more excellent cycle and rate performance. Herein, modifying VS4 with cation (Mo)/anion (O) co-doping (MVSO) enhances the electrical conductivity, generates rich sulfur and oxygen vacancies, induces the co-existence of V3+/V4+ and regulates the morphology as hollow flower-like morphology. Benefitted from the advantages of co-doping of Mo and O, MVSO delivers the excellent electrochemical properties, such as the high specific capacity (140.5 mAh g−1) under 50 mA g−1, ultralong cycling life about 1000 cycles with capacity retention ratio of 95.6%, superior rate capability (the capacity could achieve at 75.2 mAh g−1, when the current density increases to 1000 mA g−1), and low self-discharge ratio. Furthermore, the fast reaction kinetics and high capacitive process contribution for MVSO unmasked by the galvanostatic intermittent titration technique (GITT) and pesudocapaticance-like contribution analysis are highlighted. Particularly, the intrinsic Mg2+ storage mechanism and the high reversible properties caused by Mo-O co-doping is unveiled with comprehensive ex situ characterizations. These findings are supposed to open new avenues for designing cathode materials for applying in future energy storage devices.