Nanoscale Two-Dimensional Mo3N2 MXene as a Competitive-Capacity and Metallic Anode for Lithium-Ion Batteries

Abstract

This study employs first-principles calculations to systematically investigate the electrochemical performance of the two-dimensional MXene material Mo₃N₂ as an anode for lithium-ion batteries, with a focus on the effects of surface functional groups (-O and -OH) and Mo vacancies. The results show that pristine Mo₃N₂ exhibits intrinsic metallicity, a low Li-ion diffusion barrier (0.058 eV), a theoretical capacity of 339 mAh/g, and a suitable average open-circuit voltage of 0.45 V. However, surface functionalization significantly alters these properties: -O termination increases the diffusion barrier to 0.307 eV, while -OH reduces it to 0.029 eV; the capacity decreases to 308 mAh/g for Mo₃N₂O₂ and 191 mAh/g for Mo₃N₂(OH)₂. Mo vacancies are found to be easily formed (formation energy -1.08 eV) and they create a strong trapping effect that substantially hinders Li-ion diffusion. These findings reveal that the electrochemical performance of Mo₃N₂ is highly tunable by surface chemistry, and optimization requires careful control of termination groups and defect structures.