On the deterioration of ß″-alumina ceramics under electrolytic conditions

Virkar, Anil V.; Viswanathan, L.; Biswas, Don

doi:10.1007/pl00020062

Cited by 34 publications

(12 citation statements)

References 9 publications

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“…This mechanism will short-circuit the ceramic and self-discharge the cell. Similar behavior was reported in the early 1980s for Na-ion electrolyte, BASE, resulting in fast propagation of cracks and rapid failure of the ceramic. ,− The formation of isolated Li-metal agglomerates in the ceramic can also be explained by a slow degradation process occurring when a Li ion is reduced to Li metal by gaining an electron from the oxygen backbone of the ceramic (Figure c) or from the nonzero electronic conductivity, creating electron transfer from the electrode to the Li ion (Figure d). Metallic precipitates in BASE were reported at grain boundaries or at microfractured regions; , the origin of these precipitates is not well understood, but despite the low electronic conductivity, scarce electrons can transfer from one electrode and therefore reduce Na + .…”

Section: Resultssupporting

confidence: 63%

“…Further details on the mechanisms of Li dendrite formation, propagation, and dispersion in the garnet electrolyte will be reported soon. Better control of the interfacial contact between metallic lithium anode and the ceramic material will be essential to achieve homogeneous current distribution, not only during cell assembly but also during each stripping/plating step on the Li-metal anode side . Furthermore, a better understanding of dendrite formation mechanisms and their evolution in the time would be necessary to develop a new ceramic microstructure to control and reduce dendrites.…”

Section: Resultsmentioning

confidence: 99%

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Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Aguesse

Manalastas

Buannic

et al. 2017

ACS Appl. Mater. Interfaces

341

256

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All-solid-state batteries including a garnet ceramic as electrolyte are potential candidates to replace the currently used Li-ion technology, as they offer safer operation and higher energy storage performances. However, the development of ceramic electrolyte batteries faces several challenges at the electrode/electrolyte interfaces, which need to withstand high current densities to enable competing C-rates. In this work, we investigate the limits of the anode/electrolyte interface in a full cell that includes a Li-metal anode, LiFePO cathode, and garnet ceramic electrolyte. The addition of a liquid interfacial layer between the cathode and the ceramic electrolyte is found to be a prerequisite to achieve low interfacial resistance and to enable full use of the active material contained in the porous electrode. Reproducible and constant discharge capacities are extracted from the cathode active material during the first 20 cycles, revealing high efficiency of the garnet as electrolyte and the interfaces, but prolonged cycling leads to abrupt cell failure. By using a combination of structural and chemical characterization techniques, such as SEM and solid-state NMR, as well as electrochemical and impedance spectroscopy, it is demonstrated that a sudden impedance drop occurs in the cell due to the formation of metallic Li and its propagation within the ceramic electrolyte. This degradation process is originated at the interface between the Li-metal anode and the ceramic electrolyte layer and leads to electromechanical failure and cell short-circuit. Improvement of the performances is observed when cycling the full cell at 55 °C, as the Li-metal softening favors the interfacial contact. Various degradation mechanisms are proposed to explain this behavior.

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Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Aguesse

Manalastas

Buannic

et al. 2017

ACS Appl. Mater. Interfaces

341

256

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“…This current focusing results in inhomogeneous electrodeposition of Li and ultimately to the penetration of Li metal into the SE. A similar mechanism has been proposed for the penetration of sodium metal through β″-Al 2 O 3 . In the case of LLZO, cleaning of the SE surface was found to delay the onset of Li penetration to higher current densities .…”

Section: Introductionsupporting

confidence: 66%

Grain Boundary Softening: A Potential Mechanism for Lithium Metal Penetration through Stiff Solid Electrolytes

Siegel

2018

ACS Appl. Mater. Interfaces

159

161

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Models based on linear elasticity suggest that a solid electrolyte with a high shear modulus will suppress “dendrite” formation in batteries that use metallic lithium as the negative electrode. Nevertheless, recent experiments find that lithium can penetrate stiff solid electrolytes through microstructural features, such as grain boundaries. This failure mode emerges even in cases where the electrolyte has an average shear modulus that is an order of magnitude larger than that of Li. Adopting the solid-electrolyte Li7La3Zr2O12 (LLZO) as a prototype, here we demonstrate that significant softening in elastic properties occurs in nanoscale regions near grain boundaries. Molecular dynamics simulations performed on tilt and twist boundaries reveal that the grain boundary shear modulus is up to 50% smaller than in bulk regions. We propose that inhomogeneities in elastic properties arising from microstructural features provide a mechanism by which soft lithium can penetrate ostensibly stiff solid electrolytes.

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“…28 However, the balance between the lithium insertion and removal mechanisms that are outlined above produces a unique relationship between the electrodeposition current density and the stress required to extend metal filled cracks. [29][30][31][32][33][34][35][36][37][38] It should be noted that the equilibrium hydrostatic stresses which correspond to the applied overpotential are a thermodynamic upper bound on the electrochemically generated stress inside of the flaw. Stress relaxation due to extrusion (or possibly other processes) can then lead to a lower, kinetically limited stresses inside of the actual flaw.…”

mentioning

confidence: 99%

Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li₆La₃ZrTaO₁₂Garnet

Swamy

Park

Sheldon

et al. 2018

J. Electrochem. Soc.

199

193

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Solid electrolytes are considered a potentially enabling component in rechargeable batteries that use lithium metal as the negative electrode, and thereby can safely access higher energy density than available with today's lithium ion batteries. To do so, the solid electrolyte must be able to suppress morphological instabilities that lead to poor coulombic efficiency and, in the worst case, internal short circuits. In this work, lithium electrodeposition experiments were performed using single-crystal Li6La3ZrTaO12 garnet as solid electrolyte layers to investigate the factors that determine whether lithium penetration occurs through brittle inorganic solid electrolytes. In these single crystals, grain boundaries are excluded as possible paths for lithium metal propagation.However, Vickers microindentation was used to introduce sharp surface flaws of known size.Using operando optical microscopy, it was found that lithium metal penetration sometimes initiates at these controlled surface defects, and when multiple indents of varying size were present, propagates preferentially from the largest defect. However, a second class of flaws was found to be equally or more important. At the perimeter of surface current collectors, an enhanced electrodeposition current density causes lithium metal filled cracks to initiate and grow to penetration, even when the large Vickers defects are in close proximity. Modeling the electric field concentration for the experimental configurations, it was shown that a factor of 5 enhancement in field can readily occur within 10 micrometers of current collector discontinuities, which we interpret as the origin of electrochemomechanical stresses leading to failure. Such field amplification may determine the sites where supercritical surface defects dominate lithium metal propagation during electrodeposition, overriding the presence of larger defects elsewhere. Broader ContextAll-solid-state batteries can potentially store electricity at higher energy density and with greater safety than existing lithium-ion technology but require the use of lithium metal electrodes.Towards these goals, it is critical to understand possible failure modes when lithium metal electrodes are used with solid electrolytes, and especially the processes of metal dendrite formation and propagation. Here, we test the stability limits of lithium metal electrodeposition using high quality single crystals of LLZTO garnet solid electrolyte, at high current densities (5 to 10 mA/cm 2 ) equivalent to charging a battery at 1C-2C rates (1h to 0.5h charge times). We surprisingly observe that lithium metal filled cracks initiate at the edges of surface metal current collectors, rather than on millimeter-scale deliberately introduced surface cracks. At these current densities, lithium metal penetrates to short-circuit through ~2mm electrolyte thickness on the minute time scale. The results highlight a previously unrecognized failure mode for all-solidstate batteries and suggest that control of electric field distributions will be...

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On the deterioration of ß″-alumina ceramics under electrolytic conditions

Cited by 34 publications

References 9 publications

Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Grain Boundary Softening: A Potential Mechanism for Lithium Metal Penetration through Stiff Solid Electrolytes

Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li₆La₃ZrTaO₁₂Garnet

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On the deterioration of ß″-alumina ceramics under electrolytic conditions

Cited by 34 publications

References 9 publications

Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal

Grain Boundary Softening: A Potential Mechanism for Lithium Metal Penetration through Stiff Solid Electrolytes

Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li6La3ZrTaO12Garnet

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Product

Resources

About

Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li₆La₃ZrTaO₁₂Garnet