Dislocations in ceramic electrolytes for solid-state Li batteries

Abstract

High power solid-state Li batteries (SSLB) are hindered by the formation of dendrite-like structures at high current rates. Hence, new design principles are needed to overcome this limitation. By introducing dislocations, we aim to tailor mechanical properties in order to withstand the mechanical stress leading to Li penetration and resulting in a short circuit by a crack-opening mechanism. Such defect engineering, furthermore, appears to enable whisker-like Li metal electrodes for high-rate Li plating. To reach these goals, the challenge of introducing dislocations into ceramic electrolytes needs to be addressed which requires to establish fundamental understanding of the mechanics of dislocations in the particular ceramics. Here we evaluate uniaxial deformation at elevated temperatures as one possible approach to introduce dislocations. By using hot-pressed pellets and single crystals grown by Czochralski method of Li6.4La3Zr1.4Ta0.6O12 garnets as a model system the plastic deformation by more than 10% is demonstrated. While conclusions on the predominating deformation mechanism remain challenging, analysis of activation energy, activation volume, diffusion creep, and the defect structure potentially point to a deformation mechanism involving dislocations. These parameters allow identification of a process window and are a key step on the road of making dislocations available as a design element for SSLB.

Ultra-dense dislocations stabilized in high entropy oxide ceramics

“…In contrast, dislocations are rather uncommon and much less important in oxide ceramics until now. The major reason is that oxide ceramics are composed of rigid and stiff ionic/covalent bonds and can hardly tolerate the large strain energy associated with dislocations, which is quite different from metals or metallic compounds 10 , 11 . There have been many reports to induce dislocations in oxide ceramics, such as high-temperature deformation 12 – 15 .…”

60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

“…In some cases, the fundamental mobility is still low at the melting point, which puts a theoretical limit to achievable strain rates. 179 While the two above aspects describe the fundamental deformability, three further aspects need to be considered for a full perspective:…”

“…In some cases, dislocation velocities can still be below 1 mm/s at the melting point. 179 This also impacts the kinetics of deformation. Many ceramic single crystals have a particularly low starting dislocation density (e.g., as low 10 6 m −2 equaling to 1 mm between neighboring dislocations), 180 and a low dislocation velocity (e.g., nm/s).…”

“…This results in delayed dislocation multiplication and hence delayed yield as the movement required for multiplication requires long time spans 1,181 , see also panel Figure A4. The delay can be in the range of hours and, therefore, allow, for example, chemical degradation to prevail 179 when attempting to deform single crystals. At the same time, polycrystals from the same material can still be deformable -which is somewhat opposite to the behavior of the slip systems mobile at room temperature 79 .…”

Graphene in Solid-State Batteries: An Overview

“…Nevertheless, when used in a single piece (as a disk separator/pellet), ceramic SSEs do face problems such as low fracture toughness, especially when operated under stack pressures. Any tiny microscale fracture in the bulk of electrolyte provides paths for Li dendrites to sneak through that poses a risk of cell short circuit [89,90]. It is therefore desirable to increase the fracture toughness of such electrolytes.…”