VS4 anchored on Ti3C2 MXene as a high-performance cathode material for magnesium ion battery

Abstract Rechargeable magnesium batteries (rMBs) are promising techniques suitable for large-scale energy storage systems with low-cost and high safety. However, their development is severely hindered by strong coulombic effect between bivalent Mg2+ and cathode materials. In this work, two dimensional hierarchical nano-micro hybrids are synthesized by in-situ generating VS4 nanosheets on carbon-coated Ti3C2 MXene matrix (denoted as VS4@Ti3C2/C). A high-performance rMB system is built by using the hierarchical nano-micro hybrids cathode, magnesium foil anode, and 0.25 M methylpyrrolidinium chloride in 0.25 M 2PhMgCl-AlCl3/tetrahydrofuran as the electrolyte. The existence of V–C bond proves that VS4 is anchored on the surface of Ti3C2 via a strong chemical bond, rather than simply by adsorption. The unique hierarchical nano-micro structure improves the accessibility of the electrolyte and reduces the charge transfer resistance, leading to a high discharge capacity of 492 mA h g−1 at 50 mA g−1, an outstanding rate performance of 129 mA h g−1 at 1000 mA g−1, and excellent cycling performance (over 900 cycles at 500 mA g−1). Moreover, reversible intercalation of MgCl + into VS4@Ti3C2/C is revealed by investigating the evolution of the hybrids during different electrochemical states. This study will shed light on designing high-performance MXene-based cathode materials for multivalent batteries.