When thinking of batteries, the first thing that comes to mind is not typically stretchy material. However, as wearable health monitors and flexible electronics become more popular, the need for batteries with shape-shifting qualities becomes increasingly apparent. In a recent study published in ACS Energy Letters, researchers have successfully developed a lithium-ion battery with entirely stretchable components, including an electrolyte layer that can expand by an impressive 5,000%.
Creating batteries that can bend and stretch without compromising their performance is no easy task. Previous attempts at developing flexible batteries involved using conductive fabric or folding rigid components into expandable shapes, similar to origami. However, for a battery to be truly malleable, every part of it, including the electrodes and electrolyte layer, must be elastic. Unfortunately, existing stretchy battery prototypes have faced challenges such as moderate elasticity, complex assembly processes, or limited energy storage capacity over time.
Led by Wen-Yong Lai, the research team sought to overcome these limitations by developing a completely solid and stretchy battery. The novel design involved integrating the electrolyte into a polymer layer sandwiched between two flexible electrode films. To create the electrodes, a thin film of conductive paste containing silver nanowires, carbon black, and lithium-based cathode or anode materials was spread onto a plate. A layer of polydimethylsiloxane, a flexible material commonly found in contact lenses, was then applied on top of the paste. The addition of a lithium salt, a highly conductive liquid, and other stretchy polymer components resulted in a solid, rubbery layer capable of stretching to an impressive 5,000% of its original length.
When compared to traditional batteries with a liquid electrolyte, the solid stretchy battery design exhibited significant advantages. The new version demonstrated a six times higher average charge capacity at a fast-charging rate and maintained a more stable capacity over 67 charge/discharge cycles. In similar prototypes utilizing solid electrodes, the polymer electrolyte showed consistent operation over 1,000 cycles, with only a 1% drop in capacity during the first 30 cycles compared to a 16% drop for the liquid electrolyte.
While there are still improvements to be made, the development of fully stretchable and solid batteries represents a significant advancement in battery technology. This innovation could pave the way for wearable and implantable devices that can flex and move with the body, opening up new possibilities for the future of electronics and healthcare.
The integration of stretchy and solid battery components marks a promising step forward in the field of flexible electronics. By addressing key challenges and achieving impressive performance results, the research conducted by Wen-Yong Lai and the team provides valuable insights for future developments in battery technology.
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