PVP-induced synergistic engineering of interlayer, self-doping, active surface and vacancies in VS4 for enhancing magnesium ions storage and durability

Magnesium ions batteries (MIBs) provide great potential for the safety and large-scale energy storage, however, its inherent drawbacks, such as the sluggish kinetics, poor cycling life and lower specific capacities of cathode limit their practical application. Herein, PVP is innovatively incorporated with VS4 and induced synergistic engineering, including the enlarged interchain spacing, V3+ self-doping, rich sulfur vacancies and the selectively exposing active surface of (020) facets, which results in the fast kinetics of co-intercalation of Mg2+ and MgCl+, electrolyte infiltration, more active sites exposure, and the strain/stress relaxation during insertion/extraction process for the high stability of structure. Therefore, this novel design of PVP-VS4 exhibits long-term cycling stability (80% capacity retention at 5000 mA g−1 after 1500 cycles) and exceptional high-rate capability (140 mAh g−1 at 50 mA g−1 with 45 mAh g−1 at 5000 mA g−1). The fast reaction kinetics is further confirmed by galvanostatic intermittent titration technique (GITT) and density functional theory (DFT) computations. In addition, the energy storage mechanism and desirable pseudocapacitive behaviors are elucidated through series of ex situ investigations and pesudocapaticance-like contribution analysis. And PVP-VS4 delivers the higher anti-self-discharge capability cause by PVP incorporation. PVP-induced synergistic engineering opens up a new opportunity for designing a variety of effective intercalation host materials for next-generation energy storage.