A computational study on the novel defects of graphene quantum dot as a promising anode material for sodium ion battery

Highlights: • The defected graphene quantum dots are studied as an anode material in Na-ion batteries by DFT study. • The defects with an adsorbed Na atom are as an n-type-adsorbed defects which encourage oxidation of Na atom. • The cell voltage of the F and N doped defects is nearly 1.56 and 0.6 V, respectively. • F-doped defects have higher electrical conductivity, voltage, charge transfer, and reactivity. The existence of defects in the graphene quantum dots can alter their electronic properties. In this study, the interaction of sodium ion/atom with defected graphene quantum dots (dGQDs) of F₃.Gr, F₃H₃.Gr, N₃.Gr and N₃H₃.Gr as the anode material for the sodium ion batteries was investigated using density functional theory calculations. The amount of charge transfer from Na atom to F₃H₃.Gr and from F3.Gr to Na ion is about 0.23 and 0.94|e|, respectively. In the complex of Na atom with dGQDs as an n-type-adsorbed dGQD, the Fermi level shifts towards the higher energy and it can be facilitated charge transfer from Na atom to dGQDs. The estimated electrical conductivity for the complexes of Na atom with F₃.Gr and F₃H₃.Gr is 6.51 × 10⁻¹³ and 5.26 × 10⁻¹², respectively. This can result in a favorable condition in the processes of battery charge and discharge. The cell voltage belonging to F- doped defects or N- doped defects is nearly 1.54–1.58 V or 0.58–0.61 V. It is concluded that the F- doped defects are more promising anode material for sodium ion batteries compared to N- doped defects because of their lower recovery time of adsorption, higher voltage, higher reactivity and better charge transfer.