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

VS 4 is one of the most potential cathode materials candidates for magnesium ion batteries (MIBs). However, it is still challenging for suitably modifying VS 4 to make it process more excellent cycle and rate performance. Herein, modifying VS 4 with cation (Mo)/anion (O) co-doping (MVSO) enhances the electrical conductivity, generates rich sulfur and oxygen vacancies, induces the co-existence of V 3+ /V 4+ 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 Mg 2+ 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.