title: Synthesis, Crystal Chemistry, and Electrochemical Properties of Li(7-2x)La3Zr(2-x)Mo(x)O12 (x = 0.1-0.4): Stabilization of the Cubic Garnet Polymorph via Substitution of Zr(4+) by Mo(6+).
abstract: Cubic Li7La3Zr2O12 (LLZO) garnets are exceptionally well suited to be used as solid electrolytes or protecting layers in "Beyond Li-ion Battery" concepts. Unfortunately, cubic LLZO is not stable at room temperature (RT) and has to be stabilized by supervalent dopants. In this study we demonstrate a new possibility to stabilize the cubic phase at RT via substitution of Zr(4+) by Mo(6+). A Mo(6+) content of 0.25 per formula unit (pfu) stabilizes the cubic LLZO phase, and the solubility limit is about 0.3 Mo(6+) pfu. Based on the results of neutron powder diffraction and Raman spectroscopy, Mo(6+) is located at the octahedrally coordinated 16a site of the cubic garnet structure (space group Ia-3d). Since Mo(6+) has a smaller ionic radius compared to Zr(4+) the lattice parameter a0 decreases almost linearly as a function of the Mo(6+) content. The highest bulk Li-ion conductivity is found for the 0.25 pfu composition, with a typical RT value of 3.4 × 10(-4) S cm(-1). An additional significant resistive contribution originating from the sample interior (most probably from grain boundaries) could be identified in impedance spectra. The latter strongly depends on the prehistory and increases significantly after annealing at 700 °C in ambient air. Cyclic voltammetry experiments on cells containing Mo(6+) substituted LLZO indicate that the material is stable up to 6 V.
authors.affiliation: Department of Materials Research and Physics, University of Salzburg , 5020 Salzburg, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rettenwander
authors.affiliation: Institute for Chemical Technologies and Analytics, Vienna University of Technology , 1060 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Welzl
authors.affiliation: Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, University of California , Berkeley, California 94720, United States.|Department of Materials Science and Engineering, University of California , Berkeley, 94720, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.affiliation: Institute for Chemical Technologies and Analytics, Vienna University of Technology , 1060 Vienna, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fleig
authors.affiliation: Department of Materials Research and Physics, University of Salzburg , 5020 Salzburg, Austria.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Musso
authors.affiliation: Diffraction Group, Institut Laue-Langevin (ILL) , 71 avenue des Martyrs, 38000 Grenoble, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Suard
authors.affiliation: Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, University of California , Berkeley, California 94720, United States.
authors.forename: Marca M
authors.initials: MM
authors.lastname: Doeff
authors.affiliation: Department of Materials Research and Physics, University of Salzburg , 5020 Salzburg, Austria.
authors.forename: Günther J
authors.initials: GJ
authors.lastname: Redhammer
authors.affiliation: Department of Materials Research and Physics, University of Salzburg , 5020 Salzburg, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Amthauer