Experimental Visualization of Interstitialcy Diffusion of Li Ion in β-Li₂TiO₃

Monoclinic lithium metatitanate, β-Li₂TiO₃, is a member of the Li₂TiO₃ (M = Ti, Mn, Sn, Ru, and/or Ir) series and an important cation conductor for various energy applications such as Li-ion batteries and nuclear fusion reactors. Comprehensive knowledge of the crystal structure is vital to understand the Li-ion diffusion mechanism, and several possibilities were proposed previously. However, the exact crystal structure and Li-ion diffusion paths of β-Li₂TiO₃ are still unclear. Here, the results of a neutron diffraction study of high-purity ⁷Li-enriched β-Li₂TiO₃ are reported. The occupancy factor 0.033(3) and the atomic coordinates of the interstitial Li ion in the Li–O layer are successfully refined by Rietveld analysis of the time-of-flight neutron diffraction data. The three-dimensional network of Li-ion diffusion pathways is visualized by a combined technique of high-temperature neutron-diffraction and maximum-entropy methods. An interstitialcy diffusion mechanism, in which a lithium ion migrates through both the interstitial tetrahedral and lattice octahedral sites, is proposed for the Li₂TiO₃ series

Mixed alkali-ion transport and storage in atomic-disordered honeycomb layered NaKNi2TeO6

Honeycomb layered oxides constitute an emerging class of materials that show interesting physicochemical and electrochemical properties. However, the development of these materials is still limited. Here, we report the combined use of alkali atoms (Na and K) to produce a mixed-alkali honeycomb layered oxide material, namely, NaKNi2TeO6. Via transmission electron microscopy measurements, we reveal the local atomic structural disorders characterised by aperiodic stacking and incoherency in the alternating arrangement of Na and K atoms. We also investigate the possibility of mixed electrochemical transport and storage of Na+ and K+ ions in NaKNi2TeO6. In particular, we report an average discharge cell voltage of about 4 V and a specific capacity of around 80 mAh g–1 at low specific currents (i.e., < 10 mA g–1) when a NaKNi2TeO6-based positive electrode is combined with a room-temperature NaK liquid alloy negative electrode using an ionic liquid-based electrolyte solution. These results represent a step towards the use of tailored cathode active materials for “dendrite-free” electrochemical energy storage systems exploiting room-temperature liquid alkali metal alloy materials

SYNTHESIS OF PEROVSKITE-TYPE MULTICOMPONENT OXIDES BY POLYMERIZED COMPLEX METHOD

Perovskite-type multicomponent oxides such as BaTiO_3 and LaMnO_, have been synthesized by Polymerized Complex Method. Tetragonal BaTiO_3 with a small domain size formed at about 500℃ in air or 400℃ under O_2 flow. Throughout this process segregation of the individual metals was not observed. LaMnO_ powder with high surface area (>20m^2/g) was formed at about 500℃ in air or 350℃ under O2 flow