Metallic CoSb and Janus Co₂AsSb monolayers as promising anode materials for metal-ion batteries

Structural symmetry breaking plays a pivotal role in fine-tuning the properties of nano-layered materials. Here, based on the first-principles approaches we propose a Janus monolayer of metallic CoSb by breaking the out-of-plane structural symmetry. Specifically, within the CoSb monolayer by replacing the top-layer 'Sb' with 'As' atoms entirely, the Janus Co₂AsSb monolayer can be formed, whose structure is confirmed via structural optimization and ab initio molecular dynamics simulations. Notably, the Janus Co₂AsSb monolayer demonstrates stability at an elevated temperature of 1200 K, surpassing the stability of the CoSb monolayer, which remains stable only up to 900 K. We propose that both the CoSb and Janus Co₂AsSb monolayers could serve as capable anode materials for power-driven metal-ion batteries, owing to their substantial theoretical capacity and robust binding strength. The theoretical specific capacities for Li/Na reach up to 1038.28/1186.60 mA h g^-1 for CoSb, while Janus Co₂AsSb demonstrates a marked improvement in electrochemical storage capacity of 3578.69/2215.38 mA h g^-1 for Li/Na, representing a significant leap forward in this domain. The symmetry-breaking effect upgrades the CoSb monolayer, as a more viable contender for power-driven metal-ion batteries. Furthermore, electronic structure calculations indicate a notable charge transfer that augments the metallic nature, which would boost electrical conductivity. These simulations demonstrate that the CoSb and Janus Co₂AsSb monolayers have immense potential for application in the design of metal-ion battery technologies.