A metallic two-dimensional b-BS₂ monolayer as a superior Na/K-ion battery anode

Two-dimensional (2D) materials with light weight and ultra-high electrical conductivity are expected to exhibit high capacity as anodes of batteries. We have explored the curved square lattice BS₂ (b-BS₂) monolayer possessing a space group similar to the transition metal chloride (space group: P4̄M2). The electrochemical performance of the b-BS₂ monolayer as the anode for various metal-ion batteries (Li, Na, K, Mg, Ca, and Al) has been investigated. It exhibits low diffusion energy barrier, high theoretical capacity, and low open circuit voltage for Na/K-ion batteries (SIBs/PIBs). The ultrahigh energy densities of 2146.08 and 715.36 mA h g^-1 can be achieved with the stoichiometries BS₂Na₆ and BS₂K₂, respectively. Furthermore, the b-BS₂ monolayer may be synthesized on the surfaces of metal substrate materials (Ag(111), Al(111), and Au(111)). These results indicate that the b-BS₂ monolayer is a good candidate for the anode material of SIBs/PIBs.