B₃S₂ monolayer as an anode material for Na/K-ion batteries: a first-principles study

Two-dimensional (2D) materials used as anodes in metal-ion batteries have attracted increased attention due to their high specific surface area, abundant active sites and good electronic properties. Searching for 2D materials with high storage capacities and low diffusion energy barriers is one of the most effective ways to design novel anode materials. In this work, based on first-principles calculations, we design a new 2D B₃S₂ monolayer with high thermodynamic and dynamic stability. The obtained B₃S₂ monolayer has a high cohesive energy, ensuring the feasibility of experimental synthesis. These characteristics of the B₃S₂ monolayer prompt us to explore its application as an anode material. The B₃S₂ monolayer exhibits not only a metallic nature but also a low diffusion energy barrier (0.037 eV) and open-circuit voltage (0.09 V). More importantly, the B₃S₂ monolayer shows a very high theoretical capacity of 1658 mA h g^-1 as an anode material for sodium-ion batteries, which is comparable to other similar or common 2D materials. All of these intriguing properties make the B₃S₂ monolayer a promising 2D anode material for sodium-ion batteries.