Doped VS2 as a high-performance electrode material for rechargeable Mg -ion batteries

Two-dimensional (2D) vanadium disulfide (VS₂) can serve as a universal host for reversible intercalation and deintercalation of alkali and alkaline earth metal ions. However, its practical application in rechargeable metal-ion batteries is limited by its low energy density (559 Wh g^-1). Herein, the effects of O doping and C,O codoping on the electrochemical performance of 2D VS₂ used as anode for magnesium-ion batteries (MIBs) are investigated by first-principles calculations. Values of both the energy density and specific capacity increase with increasing O-doping concentration, and those of VSO are 2.17 times and 1.16 times higher than those of VS₂, respectively. However, due to the strong bond between O and Mg, the diffusion barrier of Mg atoms on 2D VSO is relatively high (1.02 eV). Further introduction of C (VSO0.75C0.25) can reduce the diffusion barrier of Mg atoms (0.80 eV) to a level comparable to that of VS₂. Meanwhile, the values of energy density and specific capacity of VSO0.75C0.25 are 1.53 times and 1.17 times those of VS₂. Our results suggest that O doping and C,O codoping of 2D VS₂ are effective strategies to improve the overall performance of MIBs and it should be possible to generalize such doping strategies to other rechargeable MIBs based on 2D transition metal dichalcogenides.