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The detailed crystal structure of cubic Li7La3Zr2O12 has been successfully determined by single-crystal X-ray structure analysis. The three-dimensional network of the Li-ion migration pathway with short Li–Li distance and occupational disordering is formed in the garnet-type framework structure. The basic unit of the pathway can be expressed as a loop constructed by the Li1 and Li2 sites. The loop links to another one, where only the Li1 site is shared by two loops as a junction.

Li2Ti6O13 was prepared from Na2Ti6O13 as a parent compound via sodium/lithium ion exchange in molten LiNO3 at 380 °C. It crystallizes in the monoclinic system, space group C2/m, and with the lattice parameters of a = 15.3065(4) Å, b = 3.74739(8) Å, c = 9.1404(2) Å, and β = 99.379(2)°. The crystal structure of Li2Ti6O13 was refined to the conventional values of R wp = 5.78% and R p = 4.44% with a fit indicator of GOF = R wp/R e = 1.66 by Rietveld analysis using powder neutron diffraction data. The crystal structure of Na2Ti6O13 was also reinvestigated using the single-crystal X-ray diffraction data with the final R value of 2.70%. The basic (Ti6O13)2− framework in Li2Ti6O13 was maintained nearly unchanged from that in the parent Na2Ti6O13. The Li occupation site in the tunnel space shifted to y = 0.5 position from the original Na site in Na2Ti6O13, and the moving resulted in the LiO4 planar coordination in Li2Ti6O13. The structural stability of Li2Ti6O13 was confirmed by bond valence sums, the data of 7Li-MAS NMR and high-temperature in situ XRD measurements, and the results of the present first-principles calculation by the FLAPW method. The electrochemical Li insertion/extraction experiments revealed the irreversible large Li insertion capacity of above 200 mAh g−1 at approximately 1.5 V for the first cycle and the stable reversible capacity of approximately 90−95 mAh g−1 during the following cycles. The total Li-ion conductivity in Li2Ti6O13 was estimated to be σtotal = 5.60 × 10−6 S cm−1 at room temperature from the results of AC-impedance measurements. This value is comparable to that in the well-known good Li-ion conducting ramsdellite-type Li2Ti3O7.

Zirconium I 4400Synthesis and Structure Analysis of Tetragonal Li7La3Zr2O12 with the Garnet-Related Type Structure. -The title compound is synthesized by solid state reaction of Li2CO3, La2O3, and ZrO2 (alumina crucible, 1253 K, 5 h). Single crystals are obtained from 1:1 mixtures of the as-prepared material and Li2CO3 as a flux (gold crucible, 1313 K, 48 h). The compound has a garnet-related structure and crystallizes in the tetragonal space group I41/acd with Z = 8 (single crystal XRD). The structure contains LaO 8 dodecahedra and ZrO 6 octahedra. Li atoms occupy the interstices of this framework structure. The bulk Li ion conductivity of tetragonal Li7La3Zr2O12 is 1.63·10 -6 S/cm, and the grain-boundary Li ion conductivity is 5.59·10 -7 S/cm at 300 K. -(AWAKA*, J.; KIJIMA, N.; HAYAKAWA, H.; AKIMOTO, J.; J. Solid State

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