Stability and comparative analysis of two-dimensional AN ₃ (A = Si, Sn) monolayers as hosts for K-ion storage: insights from first-principles calculations

Silicon (Si)- and tin (Sn)-based materials play a critical role in the green energy sector, with Si being the primary component in solar panels due to its high efficiency and widespread availability. In addition, both Si and Sn are being extensively investigated as high-capacity anode materials in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (KIBs), enhancing energy storage efficiency for sustainable applications. In this work, the potential of utilizing SiN₃ and SnN₃ monolayers as anode materials for KIBs is systematically investigated through first-principles calculations based on density functional theory (DFT). The SiN₃ and SnN₃ monolayers exhibit high cohesive energies of 6.08 and 6.81 eV per atom, respectively. Based on the results of theoretical calculations, both monolayers show excellent mechanical, dynamic, and thermal stability. Furthermore, our computational simulations show that the K-adsorbed AN₃ (A = Si, Sn) systems exhibit metallic properties, leading to excellent electronic conductivity. The diffusion barriers for K ions, as determined by the climbing-image nudged elastic band (Cl-NEB) method, are remarkably low: 0.14 eV and 0.27 eV for SiN₃ and SnN₃ monolayers, respectively. Notably, the adsorbed KSiN₃ and KSnN₃ monolayers offer several stable adsorption sites, leading to high theoretical capacities of 764.43 mAh g^-1 and 333.47 mAh g^-1, respectively. This study significantly advances the design of efficient anode materials for potassium-ion batteries.