Interchain-Expanded Vanadium Tetrasulfide with Fast Kinetics for Rechargeable Magnesium Batteries

Magnesium batteries are promising energy storage systems because of the advantages of low raw material cost, high theoretical capacity, and high operational safety properties. However, the divalent Mg²⁺ has a sluggish kinetic in the cathode materials which resulted in poor electrochemical performance. Many strategies were adopted to improve the mobility of Mg²⁺ in the host structures. In this paper, we report on the optimization of chain-like structure VS₄@reduced graphene oxide (VS₄@rGO) through expanding interchain distance to increase the ion diffusivity. By combining theoretical calculations and experimental investigations, the expansion of interchain distance and reversible intercalation of MgCl⁺ are revealed. With the fast kinetics of MgCl⁺ (instead of Mg²⁺) intercalation into expanded VS₄@rGO, higher capacity of 268.3 mA h g^-1 at 50 mA g^-1 and better rate capability of 85.9 mA h g^-1 at 2000 mA g^-1 have been obtained. In addition, the expanded VS₄@rGO framework shows a high specific capacity of 147.2 mA h g^-1 after 100 cycles and a very wide operating temperature range (-35 to 55 °C). The high discharge capacity, excellent rate capability, and broad temperature adaptability demonstrate promising application of VS₄@rGO in magnesium batteries.