Density functional theory study on the Ti3CN and Ti3CNT2 (T = O, S and F) as high capacity anode material for Na ion batteries

MXenes are the promising anode materials for the Na ion batteries (NIBs) because of their high ion capacity and low diffusion barrier to Na. The surface groups have great influence on the energy storage properties. In this paper, we performed density functional theory (DFT) calculation to study the adsorption energies, diffusion behaviors and electronic properties of Na on the Ti3CN and Ti3CNT2 monolayers (T = O, S and F functional groups). The surfaces on N and C sides of Ti3CNT2 monolayer have different adsorption behaviors to Na. The Ti3CNO2 and Ti3CNS2 exhibit better adsorptive properties to Na with the adsorption energy (Ead) of −1.702 eV and −1.626 eV, while the F functional group can reduce the value of Ead. The diffusion barriers of Na on the Ti3CNO2 and Ti3CNS2 are only 0.037 eV and 0.045 eV, which could enable the NIBs to have very fast charge/discharge rate. The theoretical capacities of Na on Ti3CNO2, Ti3CNS2 and Ti3CNF2 can reach 530 mAh g−1, 458 mAh g−1 and 516 mAh g−1, respectively. The results show that the Ti3CN, Ti3CNO2 and Ti3CNS2 can be promising anode materials for NIBs.