Daily Clinical News – Fully Stretchable Lithium-Ion Battery Paves Way for Flexible Wearable and Implantable Devices – Critical Care

Fully stretchable lithium-ion battery paves the way for flexible wearable and implantable devices

Authors: HospiMedica International employees
Published July 19, 2024

Electronics designed to bend and stretch require batteries that have the same flexible properties. Many attempts to build such batteries have used conductive fabric woven into stretchable shapes or rigid components arranged in origami-like configurations. However, for optimal flexibility, all the components of the battery, including the electrodes that store the charge and the central electrolyte layer that balances the charge, must be inherently stretchable. Existing prototypes of truly flexible batteries often exhibit only moderate flexibility, involve complex manufacturing processes, or suffer from limited energy storage capabilities that decrease with each charge cycle. This degradation in performance is often caused by poor connections between the electrolyte layer and the electrodes or by instability in the liquid electrolyte, which can shift position as the battery changes shape. Addressing these challenges, scientists have now developed a lithium-ion battery composed entirely of stretchable components that feature an electrolyte layer that can expand by 5,000%, maintaining its charging capacity even after nearly 70 charge-discharge cycles.

The fully solid, stretchable battery was created by researchers at Nanjing University of Posts and Telecommunications (Nanjing, China) by incorporating an electrolyte into a polymer layer bonded between two flexible electrode films. To construct the electrodes for this fully stretchable battery, the researchers spread a thin layer of conductive paste made of silver nanowires, carbon black, and lithium-based cathode or anode materials on a surface. They then applied a layer of polydimethylsiloxane—a flexible polymer commonly found in contact lenses—on top of the paste. Directly onto the layer, they added a lithium salt, a conductive liquid, and the ingredients needed to create a flexible polymer that solidified into a rubber-like material when activated by light. The material could stretch to 5,000 percent of its original size and efficiently transport lithium ions. The stack was topped with another electrode film, and the entire device was sealed with a protective coating.

Image: Lithium-ion battery features fully stretchable components and stable charge and discharge capacity over time (image courtesy of ACS Energy Letters 2024, DOI: 10.1021/acsenergylett.4c01254)

According to research published in ACS Energy ListsCompared to a similar stretchable battery design using a traditional liquid electrolyte, this novel solid-state battery demonstrated about six times greater average charge capacity during rapid charging. It also maintained more consistent capacity through 67 charge cycles. In comparison, other prototypes with solid electrodes showed that the polymer electrolyte performed reliably for 1,000 cycles, with only a 1% reduction in capacity in the first 30 cycles, a significant improvement over the 16% reduction seen in batteries with liquid electrolytes. Although further refinements are needed, this breakthrough in creating fully stretchable solid-state batteries represents a significant advance in the development of wearable or implantable devices that must flex and move with the human body.

Related links:
Nanjing University of Posts and Telecommunications