Two-dimensional metallic electrode materials exhibiting high electrical conductivity, excellent energy density, and minimal ion-migration barriers are essential for rechargeable ion batteries. In this study, two-dimensional TiScN, TiZrN, and TiNbN nitride MXene monolayers are predicted to be promising anode materials for rechargeable sodium-ion batteries (NIBs) based on first-principles calculations. We observed that all three monolayers are metallic compounds, and their conductivity increases with rising ion concentration. All the proposed monolayers exhibit strong interaction behavior with Na, and at the most favourable site, the adsorption energy (Eads) values are −2.964, −2.976, and −3.143 eV, and a notable amount of charge 0.285, 0.275, and 0.419 e is shared for TiScN, TiZrN, and TiNbN, respectively. As the ion concentration increases, both Eads and the charge transfer decrease. The predicted diffusion barriers for Na ions on both sides of these monolayers range from 0.016 to 0.1 eV, which are remarkably low compared to other advanced two-dimensional materials for energy storage. Furthermore, the predicted theoretical capacities are 390 mAh/g for TiScN, 272 mAh/g for TiZrN, and 461.7 mAh/g for TiNbN. These results suggest that TiNbN monolayer is a promising anode material identified so far for NIBs.
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