The structure peculiarities of K 0.9 Fe 0.9 Ti 0.1 O 2 that favor the emergence of a superionic state have been studied using neutron powder diffraction data as a function of temperature. The migration paths in the structure of both undoped and doped potassium ferrite were modeled by topological (tiling) and DFT methods. It is shown that heating of the low-temperature phase leads to increase of the ionic conductivity thanks to widening the migration channels and the appearance of thermally induced cation vacancies. The calculated migration barrier is found to not exceed 0.3 eV/ion in all phases, which is consistent with the experimental data. Doping also increases the ionic conductivity, but up to about 10% of Ti only; then the experimental activation energy even increases. The DFT modeling shows that it can be caused by growth of the regions unavailable for the mobile cations; the regions are formed around the dopant atoms.

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With the constant growth of the lithium battery market and the introduction of electric vehicles and stationary energy storage solutions, the low abundance and high price of lithium will greatly impact its availability in the future. Thus, a diversification of electrochemical energy storage technologies based on other source materials is of great relevance. Sodium is energetically similar to lithium but cheaper and more abundant, which results in some already established stationary concepts, such as Na-S and ZEBRA cells. The most significant bottleneck for these technologies is to find effective solid ionic conductors. Thus, the goal of this work is to identify new ionic conductors for Na ions in ternary Na oxides. For this purpose, the Voronoi-Dirichlet approach has been applied to the Inorganic Crystal Structure Database and some new procedures are introduced to the algorithm implemented in the programme package ToposPro. The main new features are the use of data mined values, which are then used for the evaluation of void spaces, and a new method of channel size calculation. 52 compounds have been identified to be high-potential candidates for solid ionic conductors. The results were analysed from a crystallographic point of view in combination with phenomenological requirements for ionic conductors and intercalation hosts. Of the most promising candidates, previously reported compounds have also been successfully identified by using the employed algorithm, which shows the reliability of the method.

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In this work, we provide a structural and computational investigation of the Li 2 CoPO 4 F high-voltage cathode material by means of neutron powder diffraction (SG Pnma, a = 10.4528(2) Å, b = 6.38667(10) Å, c = 10.8764(2) Å, R F = 0.0145), crystal chemistry approaches (Voronoi−Dirichlet partitioning and bond valence sums mapping), and density functional theory. The material reveals low energy barriers (0.12−0.43 eV) of Li hopping and a possible 3D channel system for Li-ion migration. It is found that only one Li per formula unit can be extracted within the potential stability window of the commercially available electrolytes. The interrelation between dimensionality, topology and energetics of Li-ion diffusion and peculiarities of the Li 2 CoPO 4 F crystal structure are discussed in detail.