Swarm-Intelligence Exploration of Na-Ion Adsorption Configuration and Diffusion Mechanism in BC ₃ Monolayers for High-Capacity Anodes

Layered two-dimensional materials are promising anode candidates for metal-ion batteries, but optimizing their performance requires a deeper understanding of the metal-ion adsorption configuration and diffusion mechanism. Previous studies have focused on adsorption with fixed sites. In this work, we introduce a global exploration method for metal-ion surface adsorption using a swarm-intelligence evolutionary algorithm. Applying this method to the BC3 monolayer, we identify double-sided, close-packed adsorption configurations, with Na5.75BC3 demonstrating a high capacity. Our analysis of Na diffusion on the BC3 anode shows that at higher Na coverage, vacancy hopping becomes the dominant diffusion mechanism, with diffusion barriers decreasing as low as 0.11 eV in Na5.75BC3. The formation of close-packed Na layers is energetically favorable due to the weakened interaction with the substrate, which lowers diffusion barriers and enhances stability, contributing to the high capacity observed in multilayer adsorption systems.