Structural and Computational Assessment of the Influence of Wet-Chemical Post-Processing of the Al-Substituted Cubic Li₇La₃Zr₂O₁₂

Journal Article · Mon Oct 08 00:00:00 EDT 2018 · ACS Applied Materials and Interfaces

DOI:https://doi.org/10.1021/acsami.8b09789· OSTI ID:1483095

Kun, Robert  ^[1]; Langer, Frederieke ^[2]; Delle Piane, Massimo  ^[3]; Ohno, Saneyuki  ^[4]; Zeier, Wolfgang G.  ^[4]; Gockeln, Michael ^[3]; Colombi Ciacchi, Lucio  ^[3]; Busse, Matthias ^[5]; Fekete, István ^[6]

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1. Univ. of Bremen (Germany); Fraunhofer Inst. for Manufacturing Technology and Advanced Materials (IFAM), Bremen (Germany)
2. Fraunhofer Inst. for Manufacturing Technology and Advanced Materials (IFAM), Bremen (Germany)
3. Univ. of Bremen (Germany)
4. Justus-Liebig-Univ., Giessen (Germany)
5. Fraunhofer Inst. for Manufacturing Technology and Advanced Materials (IFAM), Bremen (Germany); Univ. of Bremen (Germany)
6. Univ. of Szeged (Hungary)

Li₇La₃Zr₂O₁₂ (LLZO) and related compounds are considered as promising candidates for future all-solid-state Li-ion battery applications. Still, the processing of those materials into thin membranes with the right stoichiometry and crystal structure is difficult and laborious. The sensitivity of the Li-ion conductive garnets against moisture and the associated Li⁺/H⁺ cation exchange makes their processing even more difficult. Formulation of suitable polymer/ceramic hybrid solid state electrolytes could be a prosperous way to reach the future large scale production of solid state Li-ion batteries. In fact, solvent mediated and/or slurry based wet-processing of the LLZO, e.g., tape-casting, could result in irreversible Li-ion loss of the pristine material due to Li⁺/H⁺ cation exchange. The concomitant structural changes and loss in functionality in terms of Li-ion conductivity are the results of the above process. As such, in the present work a systematic study on the chemical stability and structural retention of Al-substituted LLZO in different solvents is reported. It was found that Li⁺/H⁺ exchange in LLZO occurs upon solvent immersion, and its magnitude is dependent on the availability of –OH functional groups of the solvent molecules. As a result, a larger degree of Li⁺/H⁺ exchange causes higher increase of the lattice parameter of the LLZO, determined by synchrotron diffraction analyses. The expansion of the cubic unit cell was ascertained, when Li⁺ was replaced by H⁺ in the host lattice, by ab initio computational studies. The application of the most common solvent as dispersion medium, i.e., high purity water, causes the most significant Li⁺/H⁺ exchange and, therefore, structural change, while acetonitrile was proven to be the best suitable solvent for wet postprocessing of LLZO. Finally, computational calculations suggested that the Li⁺/H⁺ exchange could result in diminished ionic, i.e., mixed Li⁺–H⁺, conductivity due to the insertion of protons with lower mobility than that of Li-ions.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: German Excellence Initiative; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1483095
• Journal Information: ACS Applied Materials and Interfaces, Vol. 10, Issue 43; ISSN 1944-8244
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
garnet type Li7La3Zr2O12
lithium ion conductor
solvent compatibility
wet-processing
composite electrolyte
all-solid-state Li-ion battery