Atomistic origin of high grain boundary resistance in solid electrolyte lanthanum lithium titanate

• Published in: Journal of Materiomics Vol. 10; no. 6; pp. 1214 - 1221
• Main Authors: Peng, Shang, Chen, Yongjin, Zhou, Xuefeng, Tang, Mingxue, Wang, Jianbo, Wang, Hua, Guo, Lin, Huang, Lujun, Yang, Wenge, Gao, Xiang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024; Elsevier
• Subjects: Cation segregation; Intergranullar glassy film; Ionic conductivity; Solid-state electrolyte; Space-charge layer; Cation segregation; Solid-state electrolyte; Intergranullar glassy film; Space-charge layer; Ionic conductivity
• ISSN: 2352-8478
• DOI: 10.1016/j.jmat.2023.12.008

Lanthanum lithium titanate is one of the promising electrolytes for solid-state lithium-ion batteries due to its high bulk ionic conductivity up to ∼10−3 S/cm. However, the practical application of this material has been bottlenecked by high grain boundary (GB) resistance, while the underlying mechanism is still under debate. Here we report a comprehensive study with direct evidence to reveal the origin of high GB resistance in La2/3–xLi3xTiO3 (LLTO). Atomic-scale observations via advanced scanning transmission electron microscopy show that the GBs are uniformly subject to subsurface segregation of La atoms to compensate for the excess surface charges. The La segregation leads to an abrupt decrease of charge carrier concentration neighboring GBs and hence is supposed to have deleterious effect on GB conductivity. The findings suggest a novel mechanism of space-charge-induced cation segregation, which shed lights on the intrinsic origin of low GB ionic conductivity in LLTO. [Display omitted] •Atomic-scale origin of the high GB resistance in LLTO was revealed through Cs-corrected STEM.•GBs in LLTO were observed as a negatively charged surface, together with the subsurface segregation of La3+.•Space-charge-induced cation segregation led to local depletion of A-site vacancies and degrade Li+ conduction through GBs.•B-site donor doping should be effective strategy to improve the Li+ conductive property of LLTO.