All-hydrogel yarn-based supercapacitor wrapped with multifunctional cotton fiber for energy storage and sensing

Abstract

Yarn-based hydrogel materials, known for their exceptional mechanical durability and soft texture, are ideal for integrating energy storage and sensing capabilities into clothing, offering a more convenient and comfortable experience for wearable bioelectronics. However, it remains challenging to equip yarn-based hydrogel materials with all necessary properties and functions simultaneously. Herein, an all-hydrogel yarn-based flexible supercapacitor, wrapped with a layer fluffy and soft sensitive film made of reduced graphene oxide-modified cotton fibers (rGCF) to achieve the dual purpose of energy storage and sensing. Firstly, a mechanically durable flexible all-hydrogel, sodium dodecyl sulfate-modified polyvinyl alcohol@copoly(acrylate-aniline) (PVA@P(AA-ANi)-SDS) yarn is created through the synergy of dynamically cross-linking and SDS-induced emulsification formation followed by freezing-copolymerization. The dynamic cross-linked hydrophobic associations of SDS allow the flexible PVA@P(AA-ANi)-SDS hydrogel yarn to exhibit excellent resistance to swelling, superior tensile properties with up to 300 % elongation at break, and a tensile strength of 1 MPa. Moreover, the obtained PVA@P(AA-ANi)-SDS yarn electrode exhibits a superior specific capacitance of 618 F g−1, and the assembled all-hydrogel PVA@P(AA-ANi)-SDS yarn-based flexible symmetric supercapacitor (SC) achieves an energy density of 37.3 Wh kg−1. Subsequently, a fluffy and soft sensitive rGCF film was wrapped around the surface of yarn-based SC to form an all-yarn-based SC-sensor. The rGCF sensitive film not only exhibits good sensitivity but also provides ample mechanical cushioning space due to its fluffy, soft, and flexible characteristics, effectively protecting the SC surface. Even under significant mechanical movement and pressure, it maintains good mechanical stability, resulting in excellent sensitivity (25.75 kPa−1) and a wide pressure detection range of up to 44 kPa.