Wearable electronic textiles that store capacitive energy are a next frontier in personalized electronics. However, the lack of industrially weavable and knittable conductive yarns in conjunction with high capacitance, limits the wide-scale application of such textiles. Here pristine soft conductive yarns are continuously produced by a scalable method with the use of twist-bundle-drawing technique, and are mechanically robust enough to be knitted to a cloth by a commercial cloth knitting machine. Subsequently, the reduced-graphene-oxide-modified conductive yarns covered with a hierarchical structure of MnO2 nanosheets and a polypyrrole thin film were used to fabricate weavable, knittable and wearable yarn supercapacitors. The resultant modified yarns exhibit specific capacitances as high as 36.6 mF cm(-1) and 486 mF cm(-2) in aqueous electrolyte (three-electrode cell) or 31 mF cm(-1) and 411 mF cm(-2) in all solid-state two-electrode cell. The symmetric solid-state supercapacitor has high energy densities of 0.0092 mWh cm(-2) and 1.1 mWh cm(-3) (both normalized to the whole device) with a long cycle life. Large energy storage textiles are fabricated by weaving our flexible all-solid-state supercapacitor yarns to a 15 cm × 10 cm cloth on a loom and knitting in a woollen wrist band to form a pattern, enabling dual functionalities of energy storage capability and wearability.

Yarn-based supercapacitors have received considerable attention recently, offering unprecedented opportunities for future wearable electronic devices (e.g., smart clothes). However, the reliability and lifespan of yarn-based supercapacitors can be seriously limited by accidental mechanical damage during practical applications. Therefore, a supercapacitor endowed with mechanically and electrically self-healing properties is a brilliant solution to the challenge. Compared with the conventional planar-like or large wire-like structure, the reconnection of the broken yarn electrode composed of multiple tiny fibers (diameter <20 μm) is much more difficult and challenging, which directly affects the restoration of electrical conductivity after damage. Herein, a self-healable yarn-based supercapacitor that ensures the reconnection of broken electrodes has been successfully developed by wrapping magnetic electrodes around a self-healing polymer shell. The strong force from magnetic attraction between the broken yarn electrodes benefits reconnection of fibers in the yarn electrodes during self-healing and thus offers an effective strategy for the restoration of electric conductivity, whereas the polymer shell recovers the configuration integrity and mechanical strength. With the design, the specific capacitance of our prototype can be restored up to 71.8% even after four breaking/healing cycles with great maintenance of the whole device's mechanical properties. This work may inspire the design and fabrication of other distinctive self-healable and wearable electronic devices.

A comprehensive review of polymer composites of BN nanotubes and nanosheets with distinguished properties.

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