First-principles study of phosphorene and graphene nanoflakes under the effectof external electric field as an anode material for Li-ion battery

Lithium ion batteries (LIBs) have been the subject of intense investigations due to their good cycling performance, high storage capacity and high energy density [1]. Despite all the studies,finding excellent anodes with good electrical conductivity and high reversible lithium storage arestill under development [2]. Therefore, in this research we investigated materials with improved properties for use in the anode electrode of Li-ion batteries, using first-principles calculations. For this purpose, two-dimensional materials such as graphene and phosphorene because of their largesurface-to-volume ratio and unique electronic properties are used. In this work the adsorption mechanism of Li metal atom and Li-ion in the absence, and presence, of a perpendicularly external electric field on the P54H18 phosphorene surface and C54H18 graphene surface (Fig 1) has beeninvestigated using M05-2X/6-31G(d,p) density functional theory (DFT) and compare the results with those of C54H18 graphene surface [3]. The structural characteristics, charge transfer, electric surface potential (ESP) maps, equilibrium distances between atom/ion and the graphene orphosphorene surface and dipole moments of the atom/ion–graphene or phosphorene complexes were investigated (Table 1). In contrast to C54H18 graphene, interactions between Li metal atoms and Li-ions with P54H18 phosphorene surface are quite strong due to its highly reactive buckledhexagonal structure (Fig 2). As a consequence of structural properties adsorption height, most stable adsorption site and energy barrier against Li diffusion are also discussed here.

Keywords:

Lithium ion batteries (LIBs) , Density functional theory (DFT) , Phosphorene , Graphene , External electric field