Investigating the electrochemical stability of Li7La3Zr2O12 solid electrolytes using field stress experiments

Stefan Smetaczek; Eva Pycha; Joseph Ring; Matthäus Siebenhofer; Steffen Ganschow; Stefan Berendts; Andreas Nenning; Markus Kubicek; Daniel Rettenwander; Andreas Limbeck; Jürgen Fleig

doi:10.1039/D1TA02983E

Investigating the electrochemical stability of Li₇La₃Zr₂O₁₂ solid electrolytes using field stress experiments†

Stefan Smetaczek,

^a Eva Pycha,^a Joseph Ring,

^a Matthäus Siebenhofer,

^a Steffen Ganschow,^b Stefan Berendts,^c Andreas Nenning,

^a Markus Kubicek,

^a Daniel Rettenwander,

^def Andreas Limbeck

^a and Jürgen Fleig

*^a

Author affiliations

* Corresponding authors

^a Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria
E-mail: Juergen.Fleig@tuwien.ac.at

^b Leibniz-Institut für Kristallzüchtung, Berlin, Germany

^c Institute of Chemistry, TU Berlin, Berlin, Germany

^d Department of Material Science and Engineering, NTNU Norwegian University of Science and Technology, Trondheim, Norway

^e International Christian Doppler Laboratory for Solid-State Batteries, NTNU Norwegian University of Science and Technology, Trondheim, Norway

^f Graz University of Technology, Institute for Chemistry and Technology of Materials, NAWI Graz, Graz, Austria

Abstract

Cubic Li₇La₃Zr₂O₁₂ (LLZO) garnets are among the most promising solid electrolytes for solid-state batteries with the potential to exceed conventional battery concepts in terms of energy density and safety. The electrochemical stability of LLZO is crucial for its application, however, controversial reports in the literature show that it is still an unsettled matter. Here, we investigate the electrochemical stability of LLZO single crystals by applying electric field stress via macro- and microscopic ionically blocking Au electrodes in ambient air. Induced material changes are subsequently probed using various locally resolved analysis techniques, including microelectrode electrochemical impedance spectroscopy (EIS), laser induced breakdown spectroscopy (LIBS), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and microfocus X-ray diffraction (XRD). Our experiments indicate that LLZO decomposes at 4.1–4.3 V vs. Li⁺/Li, leading to the formation of Li-poor phases like La₂Zr₂O₇ beneath the positively polarized electrode. The reaction is still on-going even after several days of polarization, indicating that no blocking interfacial layer is formed. The decomposition can be observed at elevated as well as room temperature and suggests that LLZO is truly not compatible with high voltage cathode materials.

This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers

Journal of Materials Chemistry A

Investigating the electrochemical stability of Li₇La₃Zr₂O₁₂ solid electrolytes using field stress experiments†

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Investigating the electrochemical stability of Li₇La₃Zr₂O₁₂ solid electrolytes using field stress experiments

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Journal of Materials Chemistry A