Monolayer Mo2C as anodes for magnesium-ion batteries.

The adsorption and diffusion behaviors of magnesium (Mg) on monolayer Mo2C have been investigated by the first principles method based on density functional theory (DFT). The structural stability and theoretical capacity of monolayer Mo2C as anodes for magnesium-ion batteries (MIBs) have also been investigated. The results show that Mg prefer to occupy the H and TC sites with the adsorption energies of - 1.439 and - 1.430, respectively, followed by B and TMo sites on Mo2C monolayer. The Mg prefers to diffuse along the H-TC-H path, furthermore, the other two possible paths (along H-B-H and H-TMo-H) also possess quite low energy barrier with the value of about 0.039 eV. The present results demonstrate that the adsorption energy per Mg atom and the volume expansion change mildly. The volume expansions change slightly from 0.7 to 7.08% with the variety of x, ranging from 0.167 to 2.0. The theoretical gravimetric capacity reaches to 469.791 mAhg-1 with relatively small deformation and expansion as x = 2.0. The results mentioned above suggest that Mo2C monolayer is one of the promising candidates for anode material of MIBs.