Bilayer and Trilayer C₃N/Blue-Phosphorene Heterostructures as Potential Anode Materials for Potassium-Ion Batteries

Two-dimensional (2D) van der Waals heterostructures outperform conventional anode materials for postlithium-ion batteries in terms of mechanical, thermal, and electrochemical properties. This study systemically investigates the performance of bilayer and trilayer C₃N/blue phosphorene (C₃N/BlueP) heterostructures as anode materials for potassium-ion batteries (KIBs) using first-principles density functional theory calculations. This study reveals that the adsorption and diffusion of K ions on bilayer and trilayer C₃N/BlueP heterostructures are markedly superior to those of their monolayer counterparts. A bilayer heterostructure (C₃N/BlueP) effectively reduces the bandgap of the BlueP monolayer (1.98 eV) to 0.02 eV, whereas trilayer heterostructures (bilayer-C₃N/BlueP and C₃N/bilayer-BlueP) exhibit metallic behavior with no bandgap. Additionally, the theoretical capacity of the bilayer and trilayer heterostructures ranges from 636.7 to 755.5 mA h g^-1, considerably higher than the theoretical capacity of other prospective 2D heterostructures for KIBs investigated in the literature. This study also shows that the heterostructures exhibit K-ion diffusion barriers as low as 0.042 eV, ensuring the relatively fast diffusion of K ions.