High capacity and mobility in germanium sulfide/graphene (GeS/Gr) van der Waals heterostructure as anode materials for sodium–ion batteries: A first-principles investigation

As a two-dimensional (2D) transition metal dichalcogenide (TMD), GeS has attracted considerable attention as an anode material for rechargeable batteries due to large surface-volume ratio, abundant adsorption sites and short diffusion paths. However, its poor electrical conductivity and large volume change upon cycling have hindered its practical application. To overcome these drawbacks, we propose a GeS/graphene (GeS/Gr) van der Waals heterostructure to be used as a high-performance composite anode in sodium-ion batteries (SIBs). Using first-principles density functional theory (DFT) calculations we systematically explore the potential of GeS/Gr heterostructure in terms of structural, electronic, mechanical and thermal properties. The introduction of the graphene layer improves the mechanical strength (Young's modulus of 415.88 Nm⁻¹), ensuring excellent structural stability which can effectively withstand large strains with less deformation. The GeS/Gr anode undergoes a semiconductor-to-metal transition upon Na adsorption, demonstrating enhanced electrical conductivity. The hybrid anode exhibits an excellent Na storage capacity of 714.27 mA h g⁻¹ and a low energy barrier of 0.05 eV for Na diffusion. Our ab-initio molecular dynamics (AIMD) simulations further confirm that Na adsorption induce no structural distortion demonstrating excellent cycling stability. Based on these results, we suggest that GeS/Gr heterostructure can be a promising anode material for SIBs.