title: Interrelationships among Grain Size, Surface Composition, Air Stability, and Interfacial Resistance of Al-Substituted Li7La3Zr2O12 Solid Electrolytes.
abstract: The interfacial resistances of symmetrical lithium cells containing Al-substituted Li7La3Zr2O12 (LLZO) solid electrolytes are sensitive to their microstructures and histories of exposure to air. Air exposure of LLZO samples with large grain sizes (∼150 μm) results in dramatically increased interfacial impedances in cells containing them, compared to those with pristine large-grained samples. In contrast, a much smaller difference is seen between cells with small-grained (∼20 μm) pristine and air-exposed LLZO samples. A combination of soft X-ray absorption (sXAS) and Raman spectroscopy, with probing depths ranging from nanometer to micrometer scales, revealed that the small-grained LLZO pellets are more air-stable than large-grained ones, forming far less surface Li2CO3 under both short- and long-term exposure conditions. Surface sensitive X-ray photoelectron spectroscopy (XPS) indicates that the better chemical stability of the small-grained LLZO is related to differences in the distribution of Al and Li at sample surfaces. Density functional theory calculations show that LLZO can react via two different pathways to form Li2CO3. The first, more rapid, pathway involves a reaction with moisture in air to form LiOH, which subsequently absorbs CO2 to form Li2CO3. The second, slower, pathway involves direct reaction with CO2 and is favored when surface lithium contents are lower, as with the small-grained samples. These observations have important implications for the operation of solid-state lithium batteries containing LLZO because the results suggest that the interfacial impedances of these devices is critically dependent upon specific characteristics of the solid electrolyte and how it is prepared.
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|‡Department of Material Sciences and Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.affiliation: §Department of Chemistry, University of California, Berkeley, California 94720, United States.|∥Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Cheng Hao
authors.initials: CH
authors.lastname: Wu
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Angelique
authors.initials: A
authors.lastname: Jarry
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: ⊥Advanced Light Source, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States.|#National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029, P. R. China.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Ye
authors.affiliation: #National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029, P. R. China.
authors.forename: Junfa
authors.initials: J
authors.lastname: Zhu
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Kostecki
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Kristin
authors.initials: K
authors.lastname: Persson
authors.affiliation: ⊥Advanced Light Source, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Guo
authors.affiliation: ‡Department of Material Sciences and Engineering, University of California, Berkeley, California 94720, United States.|∥Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Miquel
authors.initials: M
authors.lastname: Salmeron
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Guoying
authors.initials: G
authors.lastname: Chen
authors.affiliation: †Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Marca
authors.initials: M
authors.lastname: Doeff
keywords: interface; interfacial resistance; solid electrolyte; solid state battery; surface stability