[Image above] Solid-state batteries are expected to revolutionize the electric vehicle industry. But identifying promising solid-state electrolyte materials—and ways to fabricate them—are hurdles on the path to commercialization. Credit: Paul Brennan, Pixabay
Demand for batteries is on the rise as governments and companies around the world pour funding into expanding renewable energy and electric vehicle infrastructure. This increased demand is also driving research into developing safer, more efficient, and cost-effective battery technologies that can better support an electrified future than current lithium-ion batteries.
While some of this research focuses on developing entirely new battery design paradigms, such as glassy electrolytes, other scientists are exploring subtle ways to boost performance of existing technologies. For example, by applying nanocoatings to a battery’s electrodes.
It is well known that a thin coating layer between the electrolyte and electrodes can help suppress side reactions while also improving electrical contact between electrode particles. This small addition thus contributes to battery structure optimization and design.
Lithium metazirconate (Li2ZrO3 or LZO) is one material that has been investigated as a nanocoating in both traditional and solid-state lithium-ion batteries. LZO exhibits exceptional mechanical, thermal, and chemical stability, and its use as a nanocoating in batteries has resulted in enhanced cyclability and capacity retention, such as here and here.
Because of LZO’s exceptional properties, several studies have investigated the use of LZO as a solid-state electrolyte itself, rather than as just a coating. However, to date, all electrochemical testing on LZO for this application has been performed on sintered, pressed LZO discs. In application, LZO solid-state electrolytes would be formed as thin, flat, and dense sheets.
To fabricate LZO in the form of a sheet, the well-known tape casting technique is a good option. Tape casting involves forming thin and flat sheets, with a large area and thicknesses below 500 µm, from a suspension of a ceramic or metallic powder in water or nonaqueous solvents.
Despite the versatility and simplicity of this process, which make it very useful for industrial applications, researchers have not studied or optimized its use to cast thin LZO sheets.
In February 2023, researchers from several centers and universities in Argentina published a paper describing how they fabricated highly dense LZO bodies using an optimized aqueous slip casting technique.
Based on this experience, they partnered with researchers from the Instituto de Cerámica y Vidrio in Spain to develop an aqueous forming route to obtain LZO films by tape casting. The results of this collaboration are reported in a new paper published this month, August 2023.
Using knowledge from their earlier study, as well as new data gathered from slip cast samples created for this study, the researchers created optimized LZO suspensions for use in the tape casting process.
They did make a few changes compared to the slip casting process, however. For example, they added an acrylic binder agent to improve flexibility and green strength of the thin sheets. They also applied a slower heating speed during the thermal densification step to prevent the sheets from cracking during debinding.
Thanks to these optimized parameters, the researchers successfully created homogeneous, sintered, defect-free LZO tapes with thickness values close to 500 µm, bulk densities equal to about 81% of the theoretical density, and only superficial shrinkage of 19.9–22.6% after thermal treatment.
“Overall, the processing route fully described in this work could pave the way for further research on not only Li2ZrO3 tapes development for their application as SSE [solid-state electrolytes] in modern batteries, but also Li6Zr2O7 or Li8ZrO6 tapes,” the researchers conclude.
The paper, published in Journal of the European Ceramic Society, is “Aqueous tape casting of lithium metazirconate (Li2ZrO3) thin sheets” (DOI: 10.1016/j.jeurceramsoc.2023.07.050).