Computational Investigation of Two-Dimensional Vanadium Boride Compounds for Na-Ion Batteries.

Sodium (Na)-ion batteries have received widespread attention due to their low cost and good safety. The possibility of two-dimensional vanadium boride (V 2 B 2 , MBene) as the anode material for Na-ion batteries is explored by first principles. It is found that V 2 B 2 has good dynamic stability, thermodynamic stability, and conductivity. V 2 B 2 has a good performance as anode material: it can adsorb nearly 3 layers of Na ions, and the maximum capacity reaches 814 mAhg -1 . It is found that V 2 B 2 has a very low Na ion diffusion barrier, about 0.011 eV, which represents the ultrahigh ion diffusion rate of Na ions on the surface of V 2 B 2 . The average open circuit voltage of V 2 B 2 is 0.65 V, and good metallicity is maintained during the entire Na ion adsorption process. The results indicate that two-dimensional V 2 B 2 has a low diffusion barrier, low open circuit voltage, and high theoretical capacity and is a potential anode material for Na-ion batteries.