First-principle calculations of the effects of intrinsic defects in bilayer graphene as a positive electrode material for aluminum-ion batteries

Rechargeable aluminum-ion batteries draw attention in the energy storage system because of their massive gravimetric and volumetric capacities at low cost due to high abundance of raw materials. However, the suitability of positive electrode materials remains a challenge in battery development. Bilayer graphene has unique characteristics and is expected to be a good candidate for electrodes based on the lithiumand sodium-ion batteries. Furthermore, the presence of defects in graphene enhances the interaction between ion and graphene layers. We used density functional theory calculations to investigate the effects of intrinsic defects on aluminum-ion battery performance. The binding energy and interlayer distance for the pristine, defective bilayer graphene after AlCl4 intercalation ranged from-1.74 to -2.30 eV and 8.847-8.877 angstrom, respectively. We found that a high concentration of the vacancy carbon in the graphene layer will improve the working voltage of the battery meanwhile existing of the Stone Wales defect caused lacking in battery properties. AlCl4 intercalated in the pristine and defective bilayer graphene exhibited metallic characteristics according to the density of states. The stone-wales defects in the bilayer graphene could enhance the energy charge transfer. However, the AlCl4 diffusivity rate in the divacant graphene was faster than that in pristine and stone wales bilayer graphene. The diffusivity rate calculated was 8.81 x 10(-06), 8.07 x 10(-06) and 1.03 x 10(-05) cm(2)/s, accordingly. These theoretical investigations provide new insights into defect control in carbon materials to enhance aluminum-ion battery performance.