Crystal Structure and Diffusion Path in the Fast Lithium-Ion Conductor La_0.62Li_0.16TiO₃

Abstract

We report the results of a neutron powder diffraction study of the La(0.62)Li(0.16)TiO3 perovskite that determined the diffusion path of lithium cations at room temperature. At 77 K, the Li cations are located at the 2c site (Wycoff notation of the Cmmm space group) on the (002) La deficient layer, while, at room temperature, they are spread over a wide area and migrate following the 2c-4f-2c or 2c-2d-2c tie line on the (002) layer. The probability density of Li cations has a minimum between the 2c and 4f or between the 2c and 2d positions on the diffusion path in contrast to the previous reports where the bottleneck has been thought to be located at the 2c, 2d, and 4f positions. On the basis of the present structural model, the Li-cation conductivity is discussed in terms of a two-dimensional bond-percolation model for Li-cation diffusion. It was found that the vacancy at the La site is essential for the Li-cation conduction.

Arrangement of La and vacancies in La2/3TiO3 predicted by first-principles density functional calculation with cluster expansion and Monte Carlo simulation

“…Li ions jumped along diagonal directions of ab axis, and reached an energy maximum at vicinity of A-site center. The diffusion path of Li ions showed agreement with recent neutron diffraction study by Yashima et al, 17) suggesting the validity of simulated cell in Fig. 10.…”

Diffusion pathway of mobile ions and crystal structure of ionic and mixed conductors - A brief review

“…We performed a neutron powder diffraction study of the La 0.62 Li 0.16 TiO 3 perovskite that determined the crystal structure (space group: Cmmm) and diffusion path of lithium cations at room temperature. 28) At 77 K, the Li cations are located at the 2c site of the Cmmm space group on the La deficient layer at z = 1/2, while at room temperature, they are spread over a wide area and migrate following the 2c-4f-2c or 4f-2d-4f tie line along …”

Grain Boundary Analysis of the Garnet-Like Oxides Li7+X−YLa3−XAXZr2−YNbYO12 (A = Sr or Ca)

“…However, the two-dimensional lithium ion paths in this material are interrupted by grain boundaries, resulting in a high Rgb with σgrain boundary ≈ σtotal = 2 × 10 −5 Scm −1 (Inaguma et al, 1993;Stramare et al, 2003; et al, 2005;Gao et al, 2014;Moriwake et al, 2015). In contrast, the grain boundary resistance of garnet-like oxides is relatively low compared to other ion-conducting oxides because of the good lithium ion connection between grains, forming three dimensional lithium ion paths.…”