The BP ₃ monolayer as a high-capacity and rapid-diffusion anode for sodium-ion batteries: a first-principles study

The rapid development of sodium-ion batteries (SIBs) as a cost-effective alternative to lithium-ion technology demands the discovery of high-performance anode materials with large capacity, good stability, and fast ion transport. In this work, we perform a comprehensive first-principles study to evaluate the potential of the BP₃ monolayer as an anode material for SIBs. Our results show that the material exhibits excellent mechanical stability, intrinsic metallic behavior, and strong affinity toward Na-ion adsorption. In addition, Na ions diffuse on the BP₃ monolayer with a low migration barrier of 0.13 eV, suggesting fast charge/discharge kinetics. Upon full sodiation, the system retains its metallic conductivity, which is essential for efficient electron transport. The open-circuit voltage remains within a practical range during Na insertion, with an average value of 0.27 V. In particular, a theoretical storage capacity of 2325.58 mAh g^-1 is obtained, which is higher than that of many previously reported 2D anode materials. These findings highlight the BP₃ monolayer as a promising anode material for next-generation high-capacity and fast-charging sodium-ion batteries.