Mechanisms and Properties of Bismuthene and Graphene/Bismuthene Heterostructures as Anodes of Lithium-/Sodium-Ion Batteries by First-Principles Study

Compared with their bulk counterparts, bismuthene and nanocomposites of graphene and bismuthene have demonstrated improved Li/Na storage and cycling performance experimentally. However, the mechanisms are still unclear. Herein, the properties of bismuthene and graphene/bismuthene (G/Bi) heterostructures as anode materials of Li-/Na-ion batteries have been evaluated by using density functional theory. By comparing the adsorption energies (1.91/1.39 and 3.07/2.38 eV), storage capacities (384.74/384.74 and 443.12/390.99 mA h/g), diffusion barriers (0.48/0.12 and 0.14/0.10 eV), average open-circuit voltages (OCVs) (1.81/1.15 and 1.62/0.87 V), and elastic moduli (18.63 and 381.24 N/m) of Li/Na on bismuthene and G/Bi, it is found that the G/Bi heterostructure exhibits superior structural stability, higher storage capacity, larger electrical conductivity, and higher ion diffusion rate than bismuthene. In particular, the lithiation/sodiation mechanisms have been studied by analyzing the structure changes, the adsorption energies, the OCV variations, and the partial densities of states. The lithiation/sodiation mechanism shows an alloying trend in bismuthene, whereas the intercalation mechanism is seen in the G/Bi heterostructure.