Two-dimensional Ⅳ-Ⅴ compound monolayers: first principles insights for sodium ion battery anode applications

Two-dimensional materials have acquired considerable concerns in sodium-ion batteries although there are some challenges involving the number of active sites and structural stability. In this present contribution, the electrochemical nature of proposed GeSiP₂ and GeSiSb₂ monolayers as anode materials are systematically predicted through first-principles calculations. The results indicate that the compounds have the dynamic and mechanical stability according to phonon dispersion curves and cohesive energies. They are internally bonded by covalent bonds and retain better electrical conductivity after embedding sodium. The lower migration barrier of 0.074 eV from the Hollow site of six-membered ring to that of an adjacent ring can be obtained in the Sb-Si terminal case for GeSiSb₂, with the suitable diffusion coefficient of 0.69 × 10^-3 cm²/s. Additionally, there are lattice constant changes of 13.7% and 3.89% after adsorption of the maximum Na atom concentration for GeSiP₂ and GeSiSb₂, respectively, ensuring structural stability during cycling. Moreover, the maximum theoretical specific capacities of 988.58 mAh/g and 467.14 mAh/g, with suitable average open-circuit voltages of 0.48 V and 0.37 V, respectively, can be determined. All these findings illustrate that these two compounds display great potential as electrode materials for metal-ion batteries in the field of energy storage.