Two-Dimensional V₂N MXene Monolayer as a High-Capacity Anode Material for Lithium-Ion Batteries and Beyond:...

Two-dimensional metallic electrode materials with high energy density and excellent rate capability are crucial in rechargeable ion batteries. In this work, two-dimensional V₂N MXene monolayer has been predicted to be an attractive candidate anode material for rechargeable lithium, sodium, and magnesium ion batteries by first-principles calculations. We observe that V₂N monolayer is a metallic compound. The ion diffusion barriers on V₂N monolayer are predicted to be 0.025, 0.014, 0.004, and 0.058 eV for Li, Na, K, and Mg ions, respectively, which are rather low on the state-of-the-art two-dimensional energy storage materials. In addition, the calculated theoretical capacities of V₂N MXene monolayer are 925 mAh/g for Li ion, 463 mAh/g for Na ion, and 1850 mAh/g for Mg ion. The capacity of Li ions on V₂N monolayer is much higher than that of Li ions on the conventional anode graphite, and the extralarge capacity for Mg ions on V₂N monolayer is ascribed to the two-electron reaction and multilayer adsorption of Mg ions. Last, the average open circuit voltages of the V₂N MXene monolayer are also calculated to be 0.32 V for Li ions, 0.24 V for Na ions, and 0.34 V for Mg ions. These results provide a fundamental insight into electrochemical energy storage applications of two-dimensional V₂N MXene monolayer as a suitable candidate anode material for rechargeable Li, Na, and Mg ion batteries on the atomic scale.