Mechanistic Understanding of Two-Dimensional Phosphorus, Arsenic, and Antimony High-Capacity Anodes for Fast-Charging Lithium/Sodium Ion Batteries

Group-VA crystals have higher theoretical energy capacities than graphite as anode materials for Li/Na ion batteries. However, their bulks suffer from severe volume expansion and structural breakdown during lithiation or sodiation process, leading to abrupt drop of battery cycle performance. Our experimental and computational results reveal that two-dimensional (2D) group-VA crystals can preserve layered configuration without obvious structure damage. Here, we investigate the mechanism of 2D P, As, and Sb high-capacity anodes for fast charging Li/Na ion batteries by calculated binding and diffusion properties of Li/Na on group-VA monolayers. Promisingly, group-VA monolayers can give rise to greater charge/discharge capability than their corresponding parent bulk materials. This is mainly because these 2D group-VA materials with c axis free expansion hold appropriate interaction with Li/Na atoms and enjoy especially lower energy barriers than their bulks. The energy barriers calculations of monolayers under mechanical stretching indicate that the structural roughness also plays a role in hard ion mobility in bulk structure besides space constraint. We also evaluate the performance of group-VA monolayers by calculating their density of states and open circuit voltages. These results provide conclusive evidence showing that 2D group-VA materials are promising anodes for Li/Na ion batteries.