The effect of N-doping on the electronic structure property and the li and Na storage capacity of graphene nanomaterials: A first-principles study

Abstract

We performed first-principles calculations to investigate the effect of N-doping on the electronic structure property and the Li/Na storage behaviors of graphene nanomaterials. Our calculations first revealed that the N-doping treatment can effectively increase the number of C vacancy defects in graphene and the adsorption energy of a Li/Na atom on C vacancy can be largely enhanced by increasing the pyridinic-/pyrrolic-N atoms at the vacancy site. However, the reversible Li/Na capacity of the C vacancy defect was found to be largely reduced by increasing the doping level of N, which was primarily determined by the electronic structure property of the N-doped graphene structures and their strong electrostatic interactions with Li/Na. Our results clearly revealed that the enhanced Li/Na capacity by the N-doping on the graphene surface can be primarily attributed to the induced formation of a great number of C vacancy defects rather than the presence of the pyridinic-/pyrrolic-N on the basal plane. Our calculations also showed that the pyridinic-N doped graphene edges can possess a Li/Na capacity comparable to that of the N-doped C vacancy defects. Nevertheless, this excess Li/Na capacity was found to be largely reduced by the termination of the H atoms on these edge pyridinic-N groups.