Phosphorene and graphene flakes under the effect of external electric field as an anode material for high-performance lithium-ion batteries: A first-principles study

Abstract

A new phenomenon, i.e. the improvement of the adsorption energy and the diffusion of Li ion in a phosphorene monolayer under the effect of perpendicular external electric field (EEF) was studied using M06-2X/6-31G(d,p) density functional theory (DFT) framework, and also outcomes were compared with the results obtained by using of graphene. Potential energy surface (PES) scanning and analysis of origin-dependency of charged molecular systems’ energy, were used to obtain intrinsic binding energy of the charged molecular compounds within the external electric field. Our calculations revealed that, increasing the strength of field from −0.02 to 0.032 a u, caused the adsorption energies of the Li ion in the phosphorene monolayer to be increased from −64.34 to −524.60 kJmol−1 and additionally, the qualitative diffusion constant of most preferred diffusion path for Li ion on phosphorene was about 1.3 × 103 times faster than that of graphene, indicating its ultrafast and anisotropic diffusivity. The corresponding diffusion barriers were synchronously decreased from 5.57 to 2.29 kJmol−1 for the Li ion under the EEF and similar results were found for graphene. The theoretical Li capacity for a monolayer phosphorene is predicted to be 865 mAh g−1 and 973.6 mAh g−1 in the absence and presence of EEF, respectively. We have concluded that the EEF can enhance the Li theoretical capacity for a monolayer phosphorene and can increase the adsorption of Li ion onto the phosphorene and graphene monolayers, and simultaneously decrease the diffusion barriers, which in turn can improve the performance of phosphorene or graphene anode-based rechargeable ion batteries.