First-Principles Investigation of the Na+ Ion Transport Property in Oxyfluorinated Titanium(IV) Phosphate Na3Ti2P2O10F

Na+ ion batteries have now raised strong interest as replacements or alternatives of conventional Li+ ion batteries. In this work, we investigated by first-principles calculation the Na+ ion transport property of oxyfluorinated titanium(IV) phosphate Na3Ti2P2O10F, a recently reported candidate anode material. We have revealed in our simulation the 2-D ionic conduction in Na3Ti2P2O10F, with Na+ ions moving cooperatively through a combination of intra-ring and inter-ring jumps in the ab-plane. This type of mechanism is made energetically favorable by (i) the dynamic Na distribution in the ring paths and (ii) the tendency for intraring Na+ ions to assume maximum separation during actual synchronous motions. By modulating the amount of Na in the rings through aliovalent doping at Ti and P sites, significant improvement in the Na diffusion may be expected.