Bare W-based MXenes (WCrC and MoWC) anode with high specific capacity for Li and Mg-ion batteries

The emergence of double transition metal MXenes (DTMs) has addressed the challenges associated with the high molar weight and non-metallic characteristics of early transition metal MXenes. In this study, we investigate the performance of WCrC and MoWC, DTMs, as anodes in Li/Mg-ion batteries (LIBs/MIBs) using first-principles calculations. The synergistic effect between the dual metal terminals is analyzed. Our findings reveal that the W terminal provides good electronic conductivity, while the Mo/Cr terminal reduces the molar mass, leading to enhanced energy density. The theoretical capacitance values are 648.81 mAh g⁻¹ (WCrC anode) and 551.82 mAh g⁻¹ (MoWC anode) in LIB, and 432.54 mAh g⁻¹ (WCrC anode) and 367.88 mAh g⁻¹ (MoWC anode) in MIBs. Both anodes exhibit low diffusion barriers with 0.045 eV for Li and 0.079 eV for Mg. They also maintain structural rigidity throughout the battery cycle. This study highlights the crucial role of the dual metal transition terminal synergistic effect in MXenes, influencing adatom adsorption behavior, reducing molar mass, and lowering diffusion barriers. These results contribute to the advancement of MXene surface engineering and offer valuable insights for battery research.