Towards economic processing of high performance garnets – case study on zero Li excess Ga-substituted LLZO

Schwab, Christian; Häuschen, Grit; Mann, Markus; Roitzheim, Christoph; Guillon, Olivier; Fattakhova‐Rohlfing, Dina; Finsterbusch, Martin

doi:10.1039/d2ta09250f

Cited by 13 publications

(9 citation statements)

References 31 publications

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“…Areas enriched with La have less Zr, an effect attributed to Li excess. [38] The influence of the bimodal microstructure on pore morphology and distribution within the densified LLZO is investigated using CT. A 431 × 453 × 293 μm 3 volume is selected from a similar position in each fabricated sample for comparison. In Figure 3a, by labelling adjacent pores with distinct colors, it is clear that CP0 features large and interconnected pores; while, the pores are mostly isolated in the samples from CP25 to CP100.…”

Section: Resultsmentioning

confidence: 99%

“…The grey color in the maps are the pores. Areas enriched with La have less Zr, an effect attributed to Li excess 40 . The influence of the bimodal microstructure on pore morphology and distribution within the densified LLZO was investigated using CT. A 431 × 453 × 293 μm 3 volume was selected from a similar position in each fabricated sample for comparison.…”

Section: Resultsmentioning

confidence: 99%

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Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance

Jia,

Shen,

Kou

et al. 2024

Advanced Materials

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The application of solid‐state electrolytes in Li batteries has been hampered by the occurrence of Li‐dendrite‐caused short circuits. To avoid cell failure, the electrolytes can only be stressed with rather low current densities, severely restricting their performance. Since grain size and pore distributions significantly affect dendrite growth in ceramic electrolytes like Li7La3Zr2O12 and its variants, here we have proposed a “detour and buffer” strategy to bring the superiority of both coarse and fine grains into play. To validate the mechanism, a coarse/fine bimodal grain microstructure was obtained by seeding unpulverized large particles in the green body. The rearrangement of coarse grains and fine pores was fine‐tuned through changing the ratio of pulverized and unpulverized powders. The optimized bimodal microstructure, obtained when the two powders are equally mixed, allowed, without extra interface decoration, cycling for over 2000 h as the current density was increased from 1.0 mA·cm−2 gradually up to 2.0 mA·cm−2. The “detour and buffer” effects was confirmed from postmortem analysis. The complex grain boundaries formed by fine grains discourage the direct infiltration of Li. Simultaneously, the coarse grains further increase the tortuosity of the Li path. Our study sheds light on the microstructure optimization for the polycrystalline solid‐state electrolytes.This article is protected by copyright. All rights reserved

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance

Jia,

Shen,

Kou

et al. 2024

Advanced Materials

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“…The deleterious effect of excess Li in precursors resulting in tetragonal phase formation has recently been reported in the case of Ga-LLZO. 59 …”

Section: Resultsmentioning

confidence: 99%

Clarifying the Dopant Local Structure and Effect on Ionic Conductivity in Garnet Solid-State Electrolytes for Lithium-Ion Batteries

Vema,

Berge,

Nagendran

et al. 2023

Chem. Mater.

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The high Li-ion conductivity and wide electrochemical stability of Li-rich garnets (Li 7 La 3 Zr 2 O 12 ) make them one of the leading solid electrolyte candidates for solid-state batteries. Dopants such as Al and Ga are typically used to enable stabilization of the high Li + ion-conductive cubic phase at room temperature. Although numerous studies exist that have characterized the electrochemical properties, structure, and lithium diffusion in Al-and Ga-LLZO, the local structure and site occupancy of dopants in these compounds are not well understood. Two broad 27 Al or 69,71 Ga resonances are often observed with chemical shifts consistent with tetrahedrally coordinated Al/Ga in the magic angle spinning nuclear magnetic resonance (MAS NMR) spectra of both Al-and Ga-LLZO, which have been assigned to either Al and/or Ga occupying 24d and 96h/ 48g sites in the LLZO lattice or the different Al/Ga configurations that arise from different arrangements of Li around these dopants. In this work, we unambiguously show that the side products γ-LiAlO 2 and LiGaO 2 lead to the high frequency resonances observed by NMR spectroscopy and that both Al and Ga only occupy the 24d site in the LLZO lattice. Furthermore, it was observed that the excess Li often used during synthesis leads to the formation of these side products by consuming the Al/Ga dopants. In addition, the consumption of Al/Ga dopants leads to the tetragonal phase formation commonly observed in the literature, even after careful mixing of precursors. The side-products can exist even after sintering, thereby controlling the Al/Ga content in the LLZO lattice and substantially influencing the lithium-ion conductivity in LLZO, as measured here by electrochemical impedance spectroscopy.

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“…The larger implication of these observations is that while some excess Li is necessary to synthesise cubic LLZO to compensate for Li loss at elevated temperatures (1000 °C in this study) any further excess Li will instead lead to unintentional tetragonal phase formation, heterogeneity in Al distribution and γ-LiAlO2 in the final product. The deleterious effect of excess Li in precursors resulting in tetragonal phase formation has recently been reported in the case of Ga-LLZO 57 .…”

Section: Al-llzomentioning

confidence: 95%

Clarifying the local structure of dopants in garnet solid-state electrolytes for lithium-ion batteries

Vema

Berge

Nagendran

et al. 2023

Preprint

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The high Li-ion conductivity and wide electrochemical stability of Li-rich garnets (Li7La3Zr2O12) make them one of the leading solid electrolyte candidates for solid-state batteries. Dopants such as Al and Ga are typically used to enable stabilisation of the high Li+ ion-conductive cubic phase at room temperature. Although numerous studies exist that have characterized the electrochemical properties, structure, and lithium diffusion in Al- and Ga-LLZO, the local structure and site occupancy of dopants in these compounds are not well understood. Two broad 27Al or 69,71Ga resonances are often observed with chemical shifts consistent with tetrahedrally coordinated Al/Ga in the magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra of both Al- and Ga-LLZO, which have been assigned to either Al and/or Ga occupying 24d and 96h/48g sites in the LLZO lattice or to the different Al/Ga configurations that arise from different arrangements of Li around these dopants. In this work, we unambiguously show that the side products γ-LiAlO2 and LiGaO2 lead to the high frequency resonance observed by NMR spectroscopy and that both Al and Ga only occupy the 24d site in the LLZO lattice. Furthermore, it was observed that the excess Li often used during synthesis leads to the formation of these side-products by consuming the Al/Ga dopants. In addition, the consumption of Al/Ga dopants lead to the tetragonal phase formation commonly observed in the literature even after careful mixing of precursors. The side-products can exist even after sintering, thus controlling the Al/Ga content in the LLZO lattice, substantially influencing the lithium-ion conductivity in LLZO as measured here by electrochemical impedance spectroscopy.

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Towards economic processing of high performance garnets – case study on zero Li excess Ga-substituted LLZO

Abstract: In this processing study we systematically investigate the impact of lithium excess and dwell time on Ga-substituted LLZO:Ga and show that Li-excess during synthesis and processing is a critical parameter to obtain peak performance.

Cited by 13 publications

References 31 publications

Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance

Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance

Clarifying the Dopant Local Structure and Effect on Ionic Conductivity in Garnet Solid-State Electrolytes for Lithium-Ion Batteries

Clarifying the local structure of dopants in garnet solid-state electrolytes for lithium-ion batteries

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