First-principles investigation of aluminum intercalation in bilayer blue phosphorene for Al-ion battery

Here, we investigate the possibility of bilayer phosphorene as an anode material for aluminum-ion batteries using first-principles calculations. The characteristics of negative electrode materials are desirable with small volume expansion, large capacity and high mobility. We calculated the adsorption energies, optimal adsorption sites, diffusion barriers, theoretical capacities, open circuit voltages (OCVs), and structural stability of aluminum (Al) on the surface and interlayers of bilayer phosphorene. The intercalation of Al did not significantly change the volume of the bilayer phosphorene. The diffusion barrier of Al on the surface along the zigzag direction is 0.13 eV, while the diffusion barrier along the armchair direction is 0.49 eV. When Al is intercalated into the phosphorene interlayer, the diffusion barriers along the armchair and zigzag directions are 0.77 eV and 0.47 eV, respectively. It can be seen that the diffusion of Al between layers is also relatively easy. And with the increase of Al intercalation concentration, the theoretical capacity of bilayer phosphorene can reach 1047 mAhg⁻¹. These results demonstrate that bilayer phosphorene is a potential candidate as anode material for aluminum-ion batteries.