Excellent double metal MXenes MoWC anode: The synergistic effect of molybdenum and tungsten transition metal

Abstract

Double transition metal MXenes are highly desirable as anodes in ion batteries due to their larger capacitance compared to traditional single transition metal MXenes. This study investigates the effect of W and Mo on the electrochemical properties of MoWC and MoWCO2 as anodes in sodium-ion batteries, using density functional theory calculations. It is found that due to the difference in electronegativity, the double transition metal phase collects more electrons at the metal terminal than the single metal phase. This additional charge is activated and transferred to the outside of the first adsorption layer, leading to an extra Na adsorption layer. Based on this mechanism, the capacities of MoWC and MoWCO2 are determined to be 204.10 and 165.54 mAhg−1, respectively, exceeding the theoretical capacities of single metal MXenes Mo2C and W2C. Furthermore, the Na diffusion barriers in the MoWC monolayer are higher than those in the single metal phase, but they are still competitive, with values of 0.072 eV on the Mo layer and 0.055 eV on the W layer. These findings offer valuable insights for future investigations of double transition metal MXenes as potential anodes in ion batteries.