Lithium Lanthanum Titanate Single Crystals: Dependence of Lithium-Ion Conductivity on Crystal Domain Orientation

Shunsuke Kobayashi; Daisaku Yokoe; Yasuyuki Fujiwara; Kazuaki Kawahara; Yuichi Ikuhara; Akihide Kuwabara

doi:10.1021/acs.nanolett.2c01655

Lithium Lanthanum Titanate Single Crystals: Dependence of Lithium-Ion Conductivity on Crystal Domain Orientation

Nano Lett. 2022 Jul 13;22(13):5516-5522. doi: 10.1021/acs.nanolett.2c01655. Epub 2022 Jun 13.

Authors

Shunsuke Kobayashi¹, Daisaku Yokoe¹, Yasuyuki Fujiwara², Kazuaki Kawahara³, Yuichi Ikuhara^{1

3}, Akihide Kuwabara¹

Affiliations

¹ Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan.
² Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan.
³ Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8586, Japan.

PMID: 35696717
DOI: 10.1021/acs.nanolett.2c01655

Abstract

Lithium lanthanum titanate La_2/3-xLi_3xTiO₃ (LLTO) has the potential to exhibit the highest Li-ion conductivity among oxide-based electrolytes because of the fast Li-ion diffusion derived from its crystal structure. Herein, bulk Li-ion conductivity of up to σ_bulk = 4.0 × 10^-3 S/cm at 300 K, which is approximately three to four times higher than that of LLTO polycrystals, was demonstrated using LLTO single crystals, and their dependence on crystal domain orientation was examined. A change in the activation energy, which was previously obscured because of random crystal orientation, was observed at approximately 260 K. Furthermore, electron microscopy analysis indicated that the ionic conductivity of LLTOs remained higher because the region with the highest ionic conductivity was tilted away from the ideal conduction orientation. The results reported herein provide the highest conductivity in LLTO and important insights into their crystal structures, enabling higher conductivity in novel oxide-based electrolyte design.

Keywords: Crystal orientation; Li-ion conductivity; Lithium Lanthanum Titanate; Single crystal; Soled electrolyte.