Stretchable wire-shaped supercapacitors with high energy density for size-adjustable wearable electronics

•A yarn electrode has been developed by dip-coating carbon nanotubes onto the Ag-plated yarn.•The wire-shaped supercapacitors with ultrahigh energy density are fabricated with the yarn electrode.•The supercapacitors represent the available self-stretchable and size-adjustable ability.

Wire-shaped supercapacitors (WSSCs) are of considerable interest for next-generation wearable electronics. However, the poor stretchability of WSSCs based on inelastic yarn electrode seriously lead to the deficient size-adjustability of the devices. Herein, a novel kind of highly conductive, flexible and elastic yarn electrode has been put forward, which is realized by coating electro-active carbon nanotubes (CNTs) network onto the Ag-plated double-covered yarns (Ag-DCYs). On the one hand, highly conductive Ag-DCYs with “twining spring” architecture serve as the elastic substrate of the electrode. On the other hand, thin CNTs layer is uniformly wrapped on the whole yarns, which provides remarkable electrochemical capacitance for the electrode. Benefiting from the intriguing configuration, WSSCs based on the yarn electrode act as the efficient energy storage devices, which exhibit high volumetric energy density (4.17 mWh/cm3), volumetric power density (1080 mW/cm3), strong durability. More importantly, the integrated devices are randomly bendable and stretchable without the degradation of electrochemical performance. Such superior energy storage performance and steady electrochemical behaviors under high strain (150% maximum) have almost never been reported before. As a result, the WSSCs can be readily knitted with textiles and woven into different shapes, which distinctly represent the available self-stretchable and size-adjustable ability, thereby throwing light on a new avenue for the development of wearable electronics.