First-principles study on the electronic, magnetic, and Li-ion mobility properties of N-doped Ti2CO2

Abstract

First-principles calculations have been used to investigate the electronic, magnetic and Li-ion mobility properties, and theoretical capacity of N-doped Ti2CO2 with the N contents from 5 at% to 20 at%. Three possible doping types were considered: lattice substitution for C, function substitution for O, and surface adsorption on O. Our results indicate that only C-substitution doping is feasible due to its thermodynamic and dynamical stability. Upon N doping, Ti2CO2 turns into metal from semiconductor, which ensures the good electronic conductivity. A non-magnetic (NM) → ferromagnetic (FM) transition also occurs at 10 at% N content. Most importantly, the calculated lowest Li diffusion barriers are 0.33, 0.31, 0.25, and 0.23 eV, for 0 at%, 5 at%, 10 at%, and 20 at% N contents, respectively. The lower diffusion barrier shows that N-doped Ti2CO2 has a faster Li transport than pristine one. The maximum Li capacity (378–383 mAh/g) of N-doped Ti2CO2 is higher than that of most MXenes, such as Ti3C2, Nb2C, and Mo2C. These remarkable improvements in electronic conductivity, Li diffusion and storage performance suggest that N-doped Ti2CO2 is a promising anode material for Li-ion batteries.