Understanding Na-ion adsorption in nitrogen doped graphene oxide anode for rechargeable sodium ion batteries

• DFT calculations have been performed for understanding the anodic properties of N doped graphene oxide for NIBs. • Na preferably adsorbs on nearby epoxide groups with −2.38 eV which is ∼4 times greater than the E Ads of Na on the pristine graphene. • Na fully ionized about ∼(1.08–1.23|e|) near the epoxide groups while partially ionized about ∼(0.66–0.71|e|) far from the epoxide groups. • The presence of epoxide groups greatly enhances the specific capacity of graphene about 2.5–3.5 times for NIBs. Na-ion batteries (NIBs) are promising alternative to Li-ion batteries due to the abundance resources of Na and low fabrication cost. After the successful synthesis of graphene, its derivative drew huge attention as a new class of potential anode materials for NIBs. Here, nitrogen-doped graphene oxide (NDGO) has been explored as promising anode materials for high-performance NIBs. First-principles calculations have been carried out to understand the adsorption behavior, cycling stability and electrochemical properties of NDGO. The influence of epoxide groups in NDGO towards Na-ions adsorption and favorable adsorption sites on the nanosheets has also been investigated. The Na-ions near the epoxide groups were adsorbed with an adsorption energy of about −2.38 eV while far from epoxide groups, the adsorption energy is about −0.45 eV. The DOS spectra reveal that nanosheets have metallic behavior during sodiation. The specific capacities were found to be as high as 714, 1034 and 1149.32 mAh/g for mono, di and tri-epoxide groups containing NDGO respectively, which are 2.5–3.5 times higher than the hard carbon for NIBs. Moreover, the average open-circuit voltages were 0.54 V, 0.80 V and 1.04 V for mono, di and tri- epoxide groups containing NDGO respectively, which are high enough to help with suppressing the dendrite formation.