Bending impact on the performance of a flexible Li₄Ti₅O₁₂-based all-solid-state thin-film battery

Abstract

The growing demand of flexible electronic devices is increasing the requirements of their power sources. The effect of bending in thin-film batteries is still not well understood. Here, we successfully developed a high active area flexible all-solid-state battery as a model system that consists of thin-film layers of Li₄Ti₅O₁₂, LiPON, and Lithium deposited on a novel flexible ceramic substrate. A systematic study on the bending state and performance of the battery is presented. The battery withstands bending radii of at least 14 mm achieving 70% of the theoretical capacity. Here, we reveal that convex bending has a positive effect on battery capacity showing an average increase of 5.5%, whereas concave bending decreases the capacity by 4% in contrast with recent studies. We show that the change in capacity upon bending may well be associated to the Li-ion diffusion kinetic change through the electrode when different external forces are applied. Finally, an encapsulation scheme is presented allowing sufficient bending of the device and operation for at least 500 cycles in air. The results are meant to improve the understanding of the phenomena present in thin-film batteries while undergoing bending rather than showing improvements in battery performance and lifetime.

Keywords:

• Flexible all-solid-state thin-film battery
• thin-film LiPON
• thin-film Li₄Ti₅O₁₂
• bending state
• stress/strain induced
• rate performance

CLASSIFICATION:

• 50 Energy Materials
• 107 Glass and ceramic materials
• 206 Energy conversion / transport / storage / recovery
• 207 Fuel cells / Batteries / Super capacitors
• 306 Thin film / Coatings

Acknowledgments

This project has received funding from the EU Horizon 2020 research and innovation program under the MSCA grant agreement No 658057. The authors thank Knut Gandrud and Simon Hollevoet for the ALD deposition process.