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 Na 3 Ti 2 P 2 O 10 F, a recently reported candidate anode material. We have revealed in our simulation the 2-D ionic conduction in Na 3 Ti 2 P 2 O 10 F, 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.

Garnet-type Li7La3Zr2O12 has attracted attention as a promising candidate for solid electrolytes in all-solid-state lithium ion metal batteries because it exhibits high Li ion conductivity and is inert in the presence of metallic Li. However, this material is known to react with water and carbon dioxide gas, even under ambient conditions, which can cause degradation, such as a decrease in ionic conductivity. In this study, the reaction rate of the carbonation processes under both humid and dry conditions was evaluated using thermal analysis. We confirmed that carbonation did not occur at <700 K under dry conditions. The reaction kinetics were found to initially be phase-boundary controlled and then diffusion controlled, and the corresponding activation energies were estimated to be 0.5 and 0.8 eV, respectively.