First-Principles Study of Tuneable Electrochemical Performance of Zr-Based Bimetallic Mxenes as Anode Materials for Li and Na-Ion Batteries: Exploring the Synergistic Effect of Transition Metals

Abstract

In this study, we investigate the potential of bimetallic MXenes as advanced anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). Using first-principles density functional theory (DFT), we systematically examined the electrochemical performance of Zr-based bimetallic MXenes, Zr₂MC₂O₂, and M₂ZrC₂O₂ (M = Sc, Ti, V), including their structural stability, electronic properties, adsorption characteristics, and ion diffusion behavior. The strategic incorporation of 3d transition metals induces pronounced synergistic effects, significantly enhancing electronic conductivity, with Sc₂ZrC₂O₂ exhibiting the highest density of states at the Fermi level (9.375 states/eV). The computed adsorption energies confirm strong Li/Na interactions, particularly in Sc₂ZrC₂O₂, which displays exceptional adsorption affinities of −2.754 and −2.241 eV for Li and Na, respectively. Additionally, Sc₂ZrC₂O₂ achieves a remarkable theoretical specific capacity of 429 mA h g⁻¹ for NIBs and 213 mA h g⁻¹ for LIBs. Furthermore, Zr₂TiC₂O₂ exhibits the lowest average open-circuit voltage (OCV), measured at 0.33 V for NIBs and 1.23 V for LIBs. Notably, the introduction of 3d transition metals enhances Na-ion diffusion while selectively optimizing Li-ion mobility, with Sc₂ZrC₂O₂ exhibiting the lowest Li-ion diffusion barrier (0.273 eV) and Zr₂TiC₂O₂ facilitating Na-ion transport with the lowest diffusion barrier (0.309 eV). Furthermore, structural stability analysis confirms that these MXenes exhibit minimal lattice distortion and robust mechanical integrity during lithiation and sodiation. Our results highlight the synergistic effects of transition metal combinations in tailoring the electrochemical properties of MXenes, positioning them as promising candidates for high-performance anode materials in energy storage applications.