Design of Novel Wearable, Stretchable, and Waterproof Cable‐Type Supercapacitors Based on High‐Performance Nickel Cobalt Sulfide‐Coated Etching‐Annealed Yarn Electrodes

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2018-05, Vol.14 (21), p.e1704373-n/a
• Main Authors: Chen, Yuejiao, Xu, Bingang, Wen, Jianfeng, Gong, Jianliang, Hua, Tao, Kan, Chi‐Wai, Deng, Jiwei
• Format: Article
• Language: English
• Subjects: asymmetric supercapacitors; Capacitance; Coated electrodes; Cobalt sulfide; Configurations; Design; Electrochemical analysis; Electrodes; Electronic devices; Energy storage; flexible; Flux density; functionalized yarn; Innovations; Nanotechnology; Polydimethylsiloxane; Prestressing; Silicone resins; stretchable; Supercapacitors; waterproof; Yarns
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201704373

Rapid advances in functional electronics bring tremendous demands on innovation toward effective designs of device structures. Yarn supercapacitors (SCs) show advantages of flexibility, knittability, and small size, and can be integrated into various electronic devices with low cost and high efficiency for energy storage. In this work, functionalized stainless steel yarns are developed to support active materials of positive and negative electrodes, which not only enhance capacitance of both electrodes but can also be designed into stretchable configurations. The as‐made asymmetric yarn SCs show a high energy density of 0.0487 mWh cm−2 (10.19 mWh cm−3) at a power density of 0.553 mW cm−2 (129.1 mW cm−3) and a specific capacitance of 127.2 mF cm−2 under an operating voltage window of 1.7 V. The fabricated SC is then made into a stretchable configuration by a prestraining‐then‐releasing approach using polydimethylsiloxane (PDMS) tube, and its electrochemical performance can be well maintained when stretching up to a high strain of 100%. Moreover, the stretchable cable‐type SCs are stably workable under water‐immersed condition. The method opens up new ways for fabricating flexible, stretchable, and waterproof devices. Functionalized stainless steel yarns can support active materials of negative and positive electrodes to overcome the trade‐off between the electrochemical performance and mechanical properties while extending working voltage window. The cable‐type supercapacitor is fabricated by prestraining‐then‐releasing of a polydimethylsiloxane (PDMS) tube, effectively avoiding evaporation of water in gel electrolyte, possessing flexible, stretchable, and waterproof features, further exhibiting its multifunctional property.