Competing Effects in the Hydration Mechanism of a Garnet-Type Li₇La₃Zr₂O₁₂ Electrolyte

Abstract

Li-ion conducting oxides (Li 7 La 3 Zr 2 O 12 , LLZO) with a cubic garnet-type structure are among the most promising candidates to be used as solid electrolytes in all-solid-state Li batteries. However, the environmental instability of the electrolyte, induced by interaction between the material and gas molecules commonly found in air, namely, water and carbon dioxide, poses challenges for its manufacture and application. Herein, a combined experimental kinetic and thermodynamic study was performed as a function of temperature to clarify the mechanism of hydration of a garnet-type LLZO electrolyte in moist air. It was found that the kinetics of LLZO hydration is diffusion-limited and the hydration mechanism at room temperature and at higher temperatures differs. The hydration of LLZO increases up to 200 °C. Above this temperature, stagnation of water uptake is observed due to the onset of a competing dehydration process. The dehydration of LLZO takes place up to 400 °C. The partial pressure of water significantly affects the extent of hydration. Expanding this combined kinetic and thermodynamic approach to LLZO materials with a variety of chemical compositions and morphologies would allow prediction of their reactivity in a humid atmosphere and adjustment of the processing conditions accordingly to meet the requirements of technological applications.

The effects of aluminum concentration on the microstructural and electrochemical properties of lithium lanthanum zirconium oxide

“…The powders were prepared using a 3-step calcination approach, details of which can be found in numerous previous publications, especially for aluminum only substituted LLZO. 47,48 As detailed in previous publications, powders are calcined for 20 hours at 850 C and then twice for 10 hours at 1000 C. 48 However, in contrast to the synthesis of powder for pressure-less sintering reported earlier, the compositions were adapted to the specic need of hot-pressing. Since LLZO-Al0.25 and LLZO-Al0.…”

“…The presence of pressure allowed for a decrease in sintering time at comparable temperatures to traditional sintering methods, decreasing the likelihood of lithium loss. 22,23,47,48 Aer hot-pressing, each billet was cut into pellets ($1.1 mm thick) using a diamond saw. The pellets were cut to achieve parallel faces by grinding with 400 grit sandpaper and a lapping xture (PELCO 15000 micrometercontrolled lapping xture, Ted Pella) and then manually ground using 600 grit and 1200 grit sandpaper.…”

“…47,48 As detailed in previous publications, powders are calcined for 20 hours at 850 °C and then twice for 10 hours at 1000 °C. 48 However, in contrast to the synthesis of powder for pressure-less sintering reported earlier, the compositions were adapted to the specific need of hot-pressing. Since LLZO–Al0.25 and LLZO–Al0.35 showed neglectable lithium loss during calcination, no excess lithium was added before calcination (Fig.…”

A Review of Polymer‐based Solid‐State Electrolytes for Lithium‐Metal Batteries: Structure, Kinetic, Interface Stability, and Application

“…Martin Finsterbusch et al reported a recent work that systematically clarified the hydration mechanism of Li 7 La 3 Zr 2 O 12 in a humid air. [109] Specifically, the amount of Li 7 La 3 Zr 2 O 12 absorption increases with the increase of temperature before 200 °C, and the water absorption begins to stop after exceeding 200 °C. Li•H 2 O generated at room temperature limits the surface diffusion of Li 7 La 3 Zr 2 O 12 , which affects the interface reaction of solid-state batteries.…”

“…Martin Finsterbusch et al. reported a recent work that systematically clarified the hydration mechanism of Li 7 La 3 Zr 2 O 12 in a humid air [109] . Specifically, the amount of Li 7 La 3 Zr 2 O 12 absorption increases with the increase of temperature before 200 °C, and the water absorption begins to stop after exceeding 200 °C.…”