Exploring high-energy and mechanically robust anode materials based on doped graphene for lithium-ion batteries: a first-principles study

In this study, the adsorption of Li atoms on various types of doped graphene with substituents, including boron, nitrogen, sulfur and silicon atoms, has been theoretically investigated by first-principles calculations, based on the density functional theory. We discovered that the boron-doped graphene had a greatly enhanced Li-binding energy than those of graphene with other doped atoms as well as pristine graphene, which is helpful in preventing the Li atoms from clustering during charging. The Li atom preferred to be close to the doped B or Si atom, but farther away from the substituted N and S atoms, with different stable adsorption sites. This demonstrated the different chemical interactions between the Li atoms and the distinct dopants in graphene, which was confirmed by the electron density and charge transfer analysis. However, it was found that the introduction of dopant atoms in-plane with graphene reduced the mechanical strength of the graphene anode throughout the uniaxial tension simulations. Lastly, the effect of strain on the adsorption energy of the Li atoms on doped graphene was studied, and the results illustrated that tensile strain enhances the interactions between the Li atoms and the graphene anode. These results provide theoretical guidance for the discovery and fabrication of high-energy-density anode materials with desired mechanical properties.