Sodium Intercalation in Nitrogen-Doped Graphene-Based Anode: A First-Principles Study

Abstract

Density functional theory (DFT) and Monte Carlo (MC) simulations were performed to study the adsorption and distribution of Na ions on nitrogen-doped graphenes (NGs). DFT simulations revealed that both pyridinic and pyrrolic NGs enhanced Na adsorption even at higher Na concentrations by introducing electron-deficient vacancies. While Na ions tend to cluster on a pristine graphene, they separate when absorbed on pyridinic NGs due to stronger Na adsorption and Na-Na repulsion. Based on DFT energies, MC simulations were performed to study the distribution of Na on a pyridinic NG as a function of the pyridinic defect concentration and Na concentration. The average size of Na clusters decreases with increasing pyridinic defect concentration. The theoretical specific capacity increases monotonically as the pyridinic defect concentration is increased and reaches a maximum value at a concentration of ~7.5%. This theoretical study suggests that the pyridinic NGs hold promise as anode materials for sodium-ion batteries capable of enhancing Na adsorption, preventing Na clustering, and increasing the anode’s specific capacity.