Optimization of the Properties of Functionalized BC ₃ Monolayer for Superior Electrode of Solid‐State Sodium‐Ion Batteries

Abstract Solid‐state batteries offer superior safety, high energy density, and the ability to function effectively across a wide range of temperatures. Sodium‐ion (Na‐ion) solid‐state batteries are a promising alternative to lithium‐ion batteries due to sodium's abundance and low cost. A high‐quality electrode is crucial for achieving high performance in Na‐ion batteries. In this study, structural stability, electronic properties, and performance of functionalized hexagonal boron carbide (BC 3 ) are investigated for ultrathin electrodes using density functional theory (DFT). The effective adsorption of Li, Na, K, and Mg atoms at the BC 3 surface is also investigated. The BC 3 monolayer has a ≈0.8 eV indirect bandgap, which becomes metallic after Na adsorption, making it suitable for electrode applications. Additionally, the Na‐adsorbed BC 3 monolayer shows the lowest adsorption energy (−1.2 eV), which is the most stable lattice structure among others. The Na‐adsorbed BC 3 demonstrated a theoretical capacity of 1152 mAh g −1 , which is comparable with the Li‐adsorbed electrode. Moreover, the Na‐adsorbed BC 3 electrode shows a very small variation (0.18 V) for open circuit voltage (OCV), indicating this electrode is robust in terms of voltage stability. These findings show that the functionalized BC 3 ultrathin electrode is very suitable for the electrode of Na‐ion solid‐state batteries.