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Lithium metal penetration induced by electrodeposition through solid electrolytes: Example in single-crystal Li6La3ZrTaO12 garnet
Solid electrolytes potentially enable rechargeable batteries with lithium metal anodes possessing higher energy densities than today’s lithium ion batteries. To do so the solid electrolyte must suppress instabilities that lead to poor coulombic efficiency and short circuits. In this work, lithium electrodeposition was performed on single-crystal Li6La3ZrTaO12 garnets to investigate factors governing lithium penetration through brittle electrolytes. In single crystals, grain boundaries are excluded as paths for lithium metal propagation. Vickers microindentation was used to introduce surface flaws of known size. However, operando optical microscopy revealed that lithium metal penetration propagates preferentially from a different, second class of flaws. At the perimeter of surface current collectors smaller in size than the lithium source electrode, an enhanced electrodeposition current density causes lithium filled cracks to initiate and grow to penetration, even when large Vickers defects are in proximity. Modeling the electric field distribution in the experimental cell revealed that a 5-fold enhancement in field occurs within 10 micrometers of the electrode edge and generates high local electrochemomechanical stress. This may determine the initiation sites for lithium propagation, overriding the presence of larger defects elsewhere
Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li6La3ZrTaO12 Garnet
Solid electrolytes potentially enable rechargeable batteries with lithium metal anodes possessing higher energy densities than today's lithium ion batteries. To do so the solid electrolyte must suppress instabilities that lead to poor coulombic efficiency and short circuits. In this work, lithium electrodeposition was performed on single-crystal Li6La3ZrTaO12 garnets to investigate factors governing lithium penetration through brittle electrolytes. In single crystals, grain boundaries are excluded as paths for lithium metal propagation. Vickers microindentation was used to introduce surface flaws of known size. However, operando optical microscopy revealed that lithium metal penetration propagates preferentially from a different, second class of flaws. At the perimeter of surface current collectors smaller in size than the lithium source electrode, an enhanced electrodeposition current density causes lithium filled cracks to initiate and grow to penetration, even when large Vickers defects are in proximity. Modeling the electric field distribution in the experimental cell revealed that a 5-fold enhancement in field occurs within 10 micrometers of the electrode edge and generates high local electrochemomechanical stress. This may determine the initiation sites for lithium propagation, overriding the presence of larger defects elsewhere
Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li₆La₃ZrTaO₁₂ Garnet
Solid electrolytes potentially enable rechargeable batteries with lithium metal anodes possessing higher energy densities than today's lithium ion batteries. To do so the solid electrolyte must suppress instabilities that lead to poor coulombic efficiency and short circuits. In this work, lithium electrodeposition was performed on single-crystal Li₆La₃ZrTaO₁₂ garnets to investigate factors governing lithium penetration through brittle electrolytes. In single crystals, grain boundaries are excluded as paths for lithium metal propagation. Vickers microindentation was used to introduce surface flaws of known size. However, operando optical microscopy revealed that lithium metal penetration propagates preferentially from a different, second class of flaws. At the perimeter of surface current collectors smaller in size than the lithium source electrode, an enhanced electrodeposition current density causes lithium filled cracks to initiate and grow to penetration, even when large Vickers defects are in proximity. Modeling the electric field distribution in the experimental cell revealed that a 5-fold enhancement in field occurs within 10 micrometers of the electrode edge and generates high local electrochemomechanical stress. This may determine the initiation sites for lithium propagation, overriding the presence of larger defects elsewhere
Compliant Yet Brittle Mechanical Behavior of Li₂S–P₂S₅ Lithium-Ion-Conducting Solid Electrolyte
Young's modulus, hardness, and fracture toughness are measured by instrumented nanoindentation for an amorphous Li₂S–P₂S₅ Li-ion solid electrolyte. Although low elastic modulus suggests accommodation of significant chemomechanical strain, low fracture toughness can facilitate brittle crack formation in such materials.United States. Department of Energy. Office of Basic Energy Sciences (Grant DE-SC0002633
Mapping of individual dislocations with dark-field X-ray microscopy
This article presents an X-ray microscopy approach for mapping deeply
embedded dislocations in three dimensions using a monochromatic beam with a
low divergence. Magnified images are acquired by inserting an X-ray objective
lens in the diffracted beam. The strain fields close to the core of dislocations give
rise to scattering at angles where weak beam conditions are obtained. Analytical
expressions are derived for the image contrast. While the use of the objective
implies an integration over two directions in reciprocal space, scanning an
aperture in the back focal plane of the microscope allows a reciprocal-space
resolution of DQ/Q < 5 x10^-5 in all directions, ultimately enabling highprecision
mapping of lattice strain and tilt. The approach is demonstrated on
three types of samples: a multi-scale study of a large diamond crystal in
transmission, magnified section topography on a 140 mm-thick SrTiO3 sample
and a reflection study of misfit dislocations in a 120 nm-thick BiFeO3 film
epitaxially grown on a thick substrate. With optimal contrast, the half-widths at
half-maximum of the dislocation lines are 200 nm
Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li₆La₃ZrTaO₁₂ Garnet
Solid electrolytes potentially enable rechargeable batteries with lithium metal anodes possessing higher energy densities than today's lithium ion batteries. To do so the solid electrolyte must suppress instabilities that lead to poor coulombic efficiency and short circuits. In this work, lithium electrodeposition was performed on single-crystal Li₆La₃ZrTaO₁₂ garnets to investigate factors governing lithium penetration through brittle electrolytes. In single crystals, grain boundaries are excluded as paths for lithium metal propagation. Vickers microindentation was used to introduce surface flaws of known size. However, operando optical microscopy revealed that lithium metal penetration propagates preferentially from a different, second class of flaws. At the perimeter of surface current collectors smaller in size than the lithium source electrode, an enhanced electrodeposition current density causes lithium filled cracks to initiate and grow to penetration, even when large Vickers defects are in proximity. Modeling the electric field distribution in the experimental cell revealed that a 5-fold enhancement in field occurs within 10 micrometers of the electrode edge and generates high local electrochemomechanical stress. This may determine the initiation sites for lithium propagation, overriding the presence of larger defects elsewhere
Lithium Metal Penetration Induced by Electrodeposition through Solid Electrolytes: Example in Single-Crystal Li[subscript 6]La[subscript 3]ZrTaO[subscript 12] Garnet
Solid electrolytes potentially enable rechargeable batteries with lithium metal anodes possessing higher energy densities than today’s lithium ion batteries. To do so the solid electrolyte must suppress instabilities that lead to poor coulombic efficiency and short circuits. In this work, lithium electrodeposition was performed on single-crystal Li[subscript 6]La[subscript 3]ZrTaO[subscript 12] garnets to investigate factors governing lithium penetration through brittle electrolytes. In single crystals, grain boundaries are excluded as paths for lithium metal propagation. Vickers microindentation was used to introduce surface flaws of known size. However, operando optical microscopy revealed that lithium metal penetration propagates preferentially from a different, second class of flaws. At the perimeter of surface current collectors smaller in size than the lithium source electrode, an enhanced electrodeposition current density causes lithium filled cracks to initiate and grow to penetration, even when large Vickers defects are in proximity. Modeling the electric field distribution in the experimental cell revealed that a 5-fold enhancement in field occurs within 10 micrometers of the electrode edge and generates high local electrochemomechanical stress. This may determine the initiation sites for lithium propagation, overriding the presence of larger defects elsewhere.US DOE Office of Basic Energy Science (DE-SC0002633)US DOE Office of Basic Energy Science (DE-SC0018113)Austrian Science Fund (P 31437–N36
Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes
Li deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector. Four types of ion-conducting, inorganic solid electrolytes are tested: Amorphous 70/30 mol% Li2S-P2S5, polycrystalline β-Li3PS4, and polycrystalline and single-crystalline Li6La3ZrTaO12 garnet. The
nature of lithium plating depends on the proximity of the current collector to defects such as surface cracks and on the current density. Lithium plating
penetrates/infiltrates at defects, but only above a critical current density.
Eventually, infiltration results in a short circuit between the current collector and the Li-source (anode). These results do not depend on the electrolytes shear modulus and are thus not consistent with the Monroe–Newman model for “dendrites.” The observations suggest that Li-plating in pre-existing flaws produces crack-tip stresses which drive crack propagation, and an electroch-emomechanical model of plating-induced Li infiltration is proposed. Lithium short-circuits through solid electrolytes occurs through a fundamentally different process than through liquid electrolytes. The onset of Li infiltration depends on solid-state electrolyte surface morphology, in particular the defect size and density