Theoretical prediction of the O–B2S2 monolayer as a two-dimensional sodium-ion battery anode material using first-principles calculations

Abstract

Sodium-ion batteries (SIBs) have attracted considerable interest due to their affordability and abundant availability of natural resources. Nonetheless, their primary technical hurdle lies in identifying appropriate materials for anodes. This research involved modifying the surface atoms of the unaltered B₂S₂ monolayer with O atoms as external elements and methodically examining the new two-dimensional, buckling-structured O–B₂S₂ monolayer through fundamental calculations to evaluate its efficacy in sodium-ion batteries. Initial molecular dynamics simulations and phonon dispersion computations and 10 ps AIMD simulations confirm the favorable dynamic stability of the O–B₂S₂ monolayer. Notably, the O–B₂S₂ monolayer preserves its high metal content even when it absorbs sodium ions at varying concentrations, and this absorption of sodium atoms markedly enhances the O–B₂S₂ monolayer's conductivity. Furthermore, the two-dimensional O–B₂S₂ monolayer system demonstrates a reduced sodium diffusion barrier (0.179 eV) and a diminished average open circuit voltage (0.46 eV) throughout the charging and discharging phases, as revealed by the climbing image-nudged elastic-band (CI-NEB) technique. Within this framework, the O–B₂S₂ monolayer's two-dimensional storage ability can reach 910.53 mAh g⁻¹, exceeding that of numerous other two-dimensional substances, all within the voltage spectrum that restricts dendrite expansion. To sum up, the O–B₂S₂ monolayer is notable for its substantial sodium storage, minimal diffusion barrier, and appropriate open circuit voltages, indicating its potential as a high-capacity anode candidate for sodium-ion batteries.