Macroscopic and microscopic Li+ transport parameters in cubic garnet-type “Li6.5La2.5Ba0.5ZrTaO12” as probed by impedance spectroscopy and NMR

Narayanan, Sumaletha; Epp, Viktor; Wilkening, Martin; Thangadurai, Venkataraman

doi:10.1039/c2ra01042a

Cited by 64 publications

(65 citation statements)

References 52 publications

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“…where q is the elementary charge (1.602 x 10 -19 C), n is the concentration of charge carriers (found by dividing the number of Li ions per unit cell by the volume of the unit cell), k B is the Boltzmann constant (1.38 x10 -23 JK -1 ), and T is the temperature (13). The diffusion coefficient obtained using electrical and spectroscopic methods are in good agreement each other.…”

Section: Phase Characterizationsupporting

confidence: 60%

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

2013

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Garnet-type oxides, Li 5 La 3 M 2 O 12 (M = Nb, Ta) are a group of materials that exhibit high electrochemical stability and high conductivity for Li ions, making them promising electrolyte materials for all-solid-state Li-ion batteries. Li ion conductivity can continue to be increased by substituting alkaline earth and Li ions for La 3+ in the structure. Our recent work has shown a simple empirical relation between concentration of Li and ionic conductivity in several garnet-type compounds. The occupation of Li ions in various crystallographic sites also appears to control Li ion conductivity in the garnet-type structures. In the present paper, we report current progress in garnet-based Li ion electrolytes and also discuss the effect of chemical doping on ionic conductivity and chemical stability of Li 5 La 3 Nb 2 O 12 in water and organic acids.

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Section: Phase Characterizationsupporting

confidence: 60%

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

2013

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“…The peak close to 0 ppm indicates the octahedral coordination of Al, while the other peak close to 70 ppm indicates the tetrahedral coordination of Al. 8,16,[22][23][24] Geiger et al proposed that the octahedral sites occupied by Al 3+ could lead to distortion. 25 It is possible that Al 3+ substitutes for Li + sites and creates lithium vacancies in the structure which affect the structural stabilization.…”

Section: Resultsmentioning

confidence: 99%

Effect of Excess Li on the Structural and Electrical Properties of Garnet-Type Li₆La₃Ta_1.5Y_0.5O₁₂

Narayanan

Hitz

Wachsman

et al. 2015

J. Electrochem. Soc.

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Volatility of lithium during preparation of lithium-stuffed garnet-type metal oxide solid Li ion electrolytes is a common problem, which affects phase formation, ionic conductivity, mechanical strength and density. Synthesis of Li-stuffed garnets has been performed generally using the conventional solid-state reactions at elevated temperature in air. The present study describes the effect of excess LiNO 3 (2.5 to 15 wt.%) addition during the ceramic synthesis on the structural and electrical properties of garnet-type Li 6 La 3 Ta 1.5 Y 0.5 O 12 . Powder X-ray diffraction (PXRD) confirmed that cubic phase was formed in all tested cases, and there is no significant variation in lattice parameter with amount of excess LiNO 3 used. However, increasing amounts of excess lithium decreased inter-particle contact and increased grain growth during sintering, producing sharply varied microstructures. PXRD showed no secondary phase and scanning electron microscopy (SEM) analysis showed rather uniform morphology and absence of "glassy" materials at the grain-boundaries. The bulk Li ion conductivity was found to increase with amount of excess lithium, reaching a maximum room temperature conductivity of 1.62 × 10 −4 Scm −1 for the sample prepared using 10 wt.% excess LiNO 3 . Raman microscopy study indicated the presence of Li 2 CO 3 in all aged Li 6 La 3 Ta Li-stuffed garnet-type metal oxides have been considered as a potential candidate solid electrolyte material to replace conventional organic liquid based Li ion conducting electrolytes in Li-ion batteries, since members of garnet solid electrolytes exhibit high bulk ion conductivity of 10 −4 -10 −3 Scm −1 at room temperature. Furthermore, some of the garnet-type electrolytes show excellent chemical stability against reaction with elemental Li, Li-ion insertion or intercalation cathodes and high electrochemical stability window.1,2 However, the synthesis of high bulk Li ion conducting garnet-type metal oxidebased lithium ion conductors is a challenging process, very sensitive to preparation conditions used, that are not yet fully characterized. For example, Li 7 La 3 Zr 2 O 12 calcined at 1230• C results in highly conducting (7 × 10 −4 Scm −1 at room temperature) cubic phase with a space group Ia-3d whereas a calcining temperature of 980• C leads to tetragonal phase with a space group I4 1 /acd, which showed 2 orders of magnitude less conductive than cubic phase.3,4 Traditional solid-state techniques are the most commonly used to synthesize garnet-type metal oxides, but usually require the highest sintering temperature resulting in the production of large particles. [5][6][7][8] It is known that volatilization of lithium occurs in the furnace, therefore, several researchers commonly compensate with a 10 wt.% excess lithium precursors.3,9,10 Al-doped Li 7 La 3 Zr 2 O 12 prepared without adding any excess lithium salts during synthesis, but varying the processing using powder cover condition for sintering, greatly affects the morphology, grain size and density. 11Attempts h...

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“…The investigations published until now bring up the question whether the increased ion conductivity observed can solely be ascribed to Al doping. In the present study, lithium-ion dynamics of an LLZ sample, which is slightly contaminated with Al ions, is comprehensively studied by both time-domain 7 Li NMR measurements and ac impedance spectroscopy, i. e., from a microscopic and macroscopic point of view [15][16][17]. The results are compared with those of an Al-free sample crystallizing with tetragonal symmetry [11,14].…”

Section: Introductionmentioning

confidence: 99%

Li Ion Dynamics in Al-Doped Garnet-Type Li₇La₃Zr₂O₁₂ Crystallizing with Cubic Symmetry

Kuhn¹,

Choi

Robben

et al. 2012

Zeitschrift Für Physikalische Chemie

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Lithium-ion dynamics in the garnet-type solid electrolyte "Li 7 La 3 Zr 2 O 12 " (LLZ) crystallizing with cubic symmetry was probed by means of variable-temperature 7 Li NMR spectroscopy and ac impedance measurements. Li jump rates of an Al-containing sample follow Arrhenius behavior being characterized by a relatively high activation energy of 0.54(3) eV and a pre-exponential factor of 2.2(5) × 10 13 s −1 . The results resemble those which were quite recently obtained for an Al-free LLZ sample crystallizing, however, with tetragonal symmetry. Hence, most likely, the significantly higher Li conductivity previously reported for a cubic LLZ sample cannot be ascribed solely to the slight structural distortions accompanying the change of the crystal symmetry. Here, even Al impurities, acting as stabilizer for the cubic polymorph at room temperature, do not lead to the high ion conductivity reported previously.

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Macroscopic and microscopic Li+ transport parameters in cubic garnet-type “Li6.5La2.5Ba0.5ZrTaO12” as probed by impedance spectroscopy and NMR

Cited by 64 publications

References 52 publications

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

Effect of Excess Li on the Structural and Electrical Properties of Garnet-Type Li₆La₃Ta_1.5Y_0.5O₁₂

Li Ion Dynamics in Al-Doped Garnet-Type Li₇La₃Zr₂O₁₂ Crystallizing with Cubic Symmetry

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Macroscopic and microscopic Li+ transport parameters in cubic garnet-type “Li6.5La2.5Ba0.5ZrTaO12” as probed by impedance spectroscopy and NMR

Cited by 64 publications

References 52 publications

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

Recent Progress in Garnet-Type Structure Solid Li Ion Electrolytes: Composition – Structure – Ionic Conductivity Relationship and Chemical Stability Focused

Effect of Excess Li on the Structural and Electrical Properties of Garnet-Type Li6La3Ta1.5Y0.5O12

Li Ion Dynamics in Al-Doped Garnet-Type Li7La3Zr2O12 Crystallizing with Cubic Symmetry

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Effect of Excess Li on the Structural and Electrical Properties of Garnet-Type Li₆La₃Ta_1.5Y_0.5O₁₂

Li Ion Dynamics in Al-Doped Garnet-Type Li₇La₃Zr₂O₁₂ Crystallizing with Cubic Symmetry