Aging Behavior of Al- and Ga- Stabilized Li7La3Zr2O12 Garnet-Type, Solid-State Electrolyte Based on Powder and Single Crystal X-ray Diffraction

Li7La3Zr2O12 garnet (LLZO) belongs to the most promising solid electrolytes for the development of solid-state Li batteries. The stability of LLZO upon exposure to air is still a matter of discussion. Therefore, we performed a comprehensive study on the aging behavior of Al-stabilized LLZO (space gr...

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Bibliographic Details
Published in:Crystals (Basel) 2021-07, Vol.11 (7), p.721
Main Authors: Redhammer, Günther J., Tippelt, Gerold, Portenkirchner, Andreas, Rettenwander, Daniel
Format: Article
Language:English
Subjects:
Aging
Diameters
Exchanging
Humidity
Hydration
Hydrothermal treatment
Investigations
Li+-H+ cation exchange
LLZO solid-state electrolyte
Molten salt electrolytes
Occupancy
Phase transitions
prolonged aging
Single crystals
single-crystal X-ray diffraction
Solid electrolytes
Solid state
structural phase transition
Symmetry
X-ray diffraction
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Summary:Li7La3Zr2O12 garnet (LLZO) belongs to the most promising solid electrolytes for the development of solid-state Li batteries. The stability of LLZO upon exposure to air is still a matter of discussion. Therefore, we performed a comprehensive study on the aging behavior of Al-stabilized LLZO (space group (SG) Ia3¯d) and Ga-stabilized LLZO (SG I4¯3d) involving 98 powder and 51 single-crystal X-ray diffraction measurements. A Li+/H+ exchange starts immediately on exposure to air, whereby the exchange is more pronounced in samples with smaller particle/single-crystal diameter. A slight displacement of Li from interstitial Li2 (96h) toward the regular tetrahedral Li1 (24d) sites occurs in Al-stabilized LLZO. In addition, site occupancy at the 96h site decreases as Li+ is exchanged by H+. More extensive hydration during a mild hydrothermal treatment of samples at 90 °C induces a structural phase transition in Al-LLZO to SG I4¯3d with a splitting of the 24d site into two independent tetrahedral sites (i.e., 12a and 12b), whereby Al3+ solely occupies the 12a site. Li+ is preferably removed from the interstitial 48e site (equivalent to 96h). Analogous effects are observed in Ga-stabilized LLZO, which has SG I4¯3d in the pristine state.
ISSN:2073-4352
2073-4352
DOI:10.3390/cryst11070721