Zhang Huanyu, Klimpel Matthias, Wieczerzak Krzysztof, Dubey Romain, Okur Faruk, Michler Johann, Jeurgens Lars P H, Chernyshov Dmitry, van Beek Wouter, Kravchyk Kostiantyn V, Kovalenko Maksym V
Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland.
Chem Mater. 2024 Nov 5;36(22):11254-11263. doi: 10.1021/acs.chemmater.4c02351. eCollection 2024 Nov 26.
Ultrafast (UF) sintering emerges as a game-changing sintering methodology for fabricating LiLaZrO (LLZO) solid-state electrolytes, representing a pivotal stride toward the advancement and prospective commercialization of Li-garnet solid-state batteries. Despite its widespread use in the fabrication of LLZO ceramics, the chemical composition of the UF-sintered LLZO surface remains largely unexplored. This study presents an in-depth analysis of the surface chemistry of UF-sintered LLZO using comprehensive techniques, including depth-profiling X-ray photoelectron spectroscopy (XPS) and focused-ion-beam time-of-flight secondary ion mass spectroscopy (FIB-TOF-SIMS). Our investigation uncovers a striking difference between the surface of UF-sintered and conventionally sintered LLZO, revealing predominant surface contamination by LiO up to ca. 40 nm depth in the case of UF processing. Comparative synchrotron X-ray diffraction data during UF and conventional sintering elucidate the origin of surface contamination. We propose a viable solution to this issue through an additional heat treatment (HT) step at 900 °C after UF sintering, as corroborated by XPS and FIB-TOF-SIMS measurements. Furthermore, we present a comparative assessment of the electrochemical performance of Li/LLZO/Li symmetric cells based on UF-sintered LLZO pellets, both with and without the post-HT step, underscoring the pivotal role of an uncontaminated LLZO surface.
超快（UF）烧结作为一种用于制造LiLaZrO（LLZO）固态电解质的变革性烧结方法出现，代表了锂石榴石固态电池发展和未来商业化的关键一步。尽管它在LLZO陶瓷制造中广泛使用，但UF烧结的LLZO表面的化学成分在很大程度上仍未被探索。本研究使用包括深度剖析X射线光电子能谱（XPS）和聚焦离子束飞行时间二次离子质谱（FIB-TOF-SIMS）在内的综合技术，对UF烧结的LLZO的表面化学进行了深入分析。我们的研究发现UF烧结的LLZO表面与传统烧结的LLZO表面之间存在显著差异，发现在UF加工情况下，LiO在高达约40 nm深度处存在主要的表面污染。UF烧结和传统烧结过程中的同步加速器X射线衍射对比数据阐明了表面污染的来源。通过在UF烧结后在900°C进行额外的热处理（HT）步骤，我们提出了一个解决该问题的可行方案，XPS和FIB-TOF-SIMS测量证实了这一点。此外，我们对基于UF烧结的LLZO颗粒的Li/LLZO/Li对称电池的电化学性能进行了比较评估，该颗粒有或没有HT后处理步骤，强调了未受污染的LLZO表面的关键作用。
