Tuning the electrochemical performance of Cr2B2 MBene anodes for Li and Na-ion batteries through F and Cl-functionalization: A DFT and AIMD study

In an era in which sustainable energy sources and electric vehicles are prevalent, the development of efficient anode materials is paramount to address the pressing demand for improved energy storage technologies. After the graphene revolution, many other 2D materials such as graphene, MXene (atomically thin layer of Transition Metal Carbide/Nitride/Carbonitride), TMDC (Transition Metal Dichalcogenide), and MBene (atomically thin layer of Transition Metal Borides) have emerged as potential high-performance anode materials. A recent study demonstrated the possibility of synthesizing chromium-based MBenes for the first time, and the electrochemical performance of Cr2B2 as a potential anode material has also been studied theoretically. Inspired by this, the current study utilized density functional theory and ab initio molecular dynamics simulations to probe the role of Cl and F-functionalization of Cr2B2 MBenes as anode materials for rechargeable lithium-ion batteries (LIB) and sodium-ion batteries (NIB). The electronic structure, adsorption, diffusion, and storage capacity of Li (Lithium) and Na (Sodium) were systematically investigated. This study revealed that Cr2B2F2 and Cr2B2Cl2 exhibit excellent conductivity due to their intrinsic metallic properties. In addition, they have low diffusion energy barriers for Li and Na ions (0.13/0.14 and 0.20/0.20 eV for Cr2B2F2 and Cr2B2Cl2, respectively) facilitating rapid charge/discharge rates. The calculations further unveiled a notable Li-ion storage capacity of 818 mAh g-1 for 2D Cr2B2Cl2, accompanied by a moderate open-circuit voltage (OCV) range of 0.38 V to 0.98 V, illustrating its potential as a superior anodic material for LIBs. Similarly, Cr2B2F2 demonstrated a substantial Na-ion storage capacity of 655 mAh g-1, coupled with a reasonably ranged average OCV of 0.20 V to 0.71 V, positioning it as a compelling candidate for NIBs. In all, this investigation has identified two superior electrode materials for alkali-ion batteries, which can spark additional interest in exploring MBene as a promising candidate for advancing next-generation anode materials.