Double transition metal MXenes as anode materials for high-capacity multivalent metal-ion batteries: a computational study

Abstract

The growing global energy crisis and increasing demand for sustainable energy storage solutions have intensified the search for efficient and high-capacity battery technologies. Conventional lithium-ion batteries, although widely used, face challenges of resource scarcity, limited energy density, and environmental concerns. As a promising alternative, multivalent metal-ion (e.g., Mg²⁺, Zn²⁺, and Al³⁺) batteries offer higher charge storage capabilities and improved cost-effectiveness compared to monovalent Li⁺, Na⁺, and K⁺-based metal-ion batteries. Here, we explore the potential of novel double-transition-metal (DTM) MXenes as electrode materials for multivalent metal-ion batteries using density functional theory (DFT). Geometrical stability, electronic properties, ion adsorption behavior, and electrolyte compatibility are systematically analyzed to evaluate their electrochemical performance. Our results reveal that these MXenes exhibit excellent specific capacities of 3096.64, 2064.43, and 688.14 mAh per g (VNbC); 1978.76, 1319.17, and 439.72 mAh per g (VTaC); and 844.14, 1125.52, and 375.17 mAh per g (NbTaC) for Al, Mg, and Zn, respectively. Additionally, we demonstrate low diffusion barriers of 0.26, 0.13, and 0.19 eV (on VNbC); 0.25, 0.10, and 0.16 eV (on VTaC); and 0.18, 0.06, and 0.16 eV (on NbTaC) for Al, Mg, and Zn, respectively. This study shows that the VNbC monolayer provides a much higher Al³⁺-ion storage capacity than that of the widely commercialized graphite in lithium-ion batteries. This investigation unearths key insights into the fundamental mechanisms governing ion intercalation in DTM MXene-based anodes, which is encouraging for their application in advanced rechargeable battery technologies.