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 T_C sites with the adsorption energies of - 1.439 and - 1.430, respectively, followed by B and T_Mo sites on Mo₂C monolayer. The Mg prefers to diffuse along the H-T_C-H path, furthermore, the other two possible paths (along H-B-H and H-T_Mo-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.