Unveiling the Potential of Boron-Rich Two-Dimensional TiB₆ Monolayer as a High-Performance Anode Material for Sodium-Ion Batteries: Insights into Correlation Mechanisms for Multi-Ion Migration

The B-rich two-dimensional TiB6 monolayers hasa theoretical capacity of up to 951.23 mAh g(-1) andpossesses low diffusion barriers (0.178 eV) and average open-circuitvoltages (0.103 V). Boron-rich materials have emerged as a promising classof anodematerials, because of their unique structural and electrochemicalproperties. In this study, we investigate the potential of a boron-richtwo-dimensional (2D) TiB6 monolayer as an anode materialfor SIBs using first-principles calculations and crystal structurepredictions. Our findings reveal that the TiB6 monolayer,with its unique B-rich structure, can not only accommodate largerNa ions but also shield metal cations, thereby weakening the repulsionbetween Na ions and metal cations and increasing the capacity of theanode. We demonstrate that the TiB6 fully sodiumated phaseis TiB6Na4, which exhibits an extremely hightheoretical capacity of 951.23 mAh g(-1). Moreover,our simulations show that the TiB6 monolayer has a lowerdiffusion barrier and average open circuit voltage, compared withother anode materials. Additionally, our systematic calculations ofion diffusion reveal that the migration of multiple Na ions on theTiB(6) monolayer is mainly governed by a correlation mechanism,where the diffusing Na ions can push others to migrate, resultingin an extremely low diffusion energy barrier. These findings highlightthe potential of the boron-rich 2D TiB6 monolayer as ahigh-performance anode material for SIBs and shed light on the importanceof boron-rich materials in the search for next-generation batterymaterials.