Microscopic dynamics of lithium diffusion in single crystal of the solid-state electrolyte La
Li
TiO
(x = 0.13) studied by quasielastic neutron scattering
中性子準惰性散乱による単結晶固体電解質La
Li
TiO
(x = 0.13)におけるリチウム拡散の微視的ダイナミクス
松浦 直人*; 藤原 靖幸*; 森分 博紀*; 尾原 幸治*; 川北 至信

Matsuura, Masato*; Fujiwara, Yasuyuki*; Moriwake, Hiroki*; Ohara, Koji*; Kawakita, Yukinobu
Quasielastic neutron scattering (QENS) measurements combined with first principles based molecular dynamics calculations were conducted to study the dynamics of Li
ions in a solid-state electrolyte La
Li
TiO
(LLTO) with
. By using a large
Li-enriched single crystal sample, a QENS signal was clearly observed along the three principal axes [110], [111], and [001] at a temperature (
) of 600 K. Wave vector dependence of the linewidth of the QENS signal along each direction was explained well using the Chudley-Elliot model for jumps between the A sites of the perovskite lattice through the bottleneck square, which was also supported by molecular dynamics calculations. The estimated self-diffusion coefficient of Li
(
) in the ab plane was slightly larger than that along the c axis, suggesting quasi-isotropic diffusion, that is, the three-dimensional diffusion of Li
ions. The decrease in
with decreasing
was reasonably explained by a thermal activation process with the activation energy determined from ionic-conductivity measurements. Furthermore, the estimated values of the self-diffusion coefficient are comparable to those in the sulfide-based Li
ion conductor, Li
P
S
, with 10 times larger ionic conductivity, which clarifies how to understand the Li conduction mechanism in LLTO and Li
P
S
in a unified manner.