Theoretical Investigation of a Novel Two-Dimensional Non-MXene MoC as a Prospective Anode Material for Li- and Na-Ion Batteries.

A new two-dimensional (2D) non-MXene transition metal carbide, MoC, was found using the USPEX code. Comprehensive first-principles calculations show that the MoC monolayer exhibits thermal, dynamic, and mechanical stability, which can ensure excellent durability in practical applications. The optimized structures of Li@(3×3)-MoC ( = 1-36) and Na@(3×3)-MoC ( = 1-32) were identified as prospective anode materials. The metallic MoC sheet exhibits low diffusion barriers of 0.190 eV for Li and 0.118 eV for Na and low average open circuit voltages of 0.31-0.55 V for Li and 0.18-0.48 V for Na. When adsorbing two layers of adatoms, the theoretical energy capacities are 344 and 306 mA h g for Li and Na, respectively, which are comparable to that of commercial graphite. Moreover, the MoC substrate can maintain structural integrity during the lithiation or sodiation process at high temperature. Considering these features, our proposed MoC slab is a potential candidate as an anode material for future Li- and Na-ion batteries.