Flexible Polypyrrole@Fe2O3@Stainless Steel Yarn Composite Electrode for Symmetric Thread‐Like Supercapacitor with Extended Operating Voltage Window in Li2SO4‐Based Aqueous Electrolyte

• Published in: Advanced sustainable systems (Online) 2020-11, Vol.4 (11), p.n/a
• Main Authors: Zuo, Wusheng, Zang, Limin, Wang, Xue, Liu, Qifan, Qiu, Jianhui, Liang, Chunliu, Liu, Xin, Yang, Chao
• Format: Article
• Language: English
• Subjects: iron oxide nanosheets; polypyrroles; thread‐like supercapacitors
• ISSN: 2366-7486; 2366-7486
• DOI: 10.1002/adsu.202000173

A flexible symmetric thread‐like supercapacitor (TSC) with high operating voltage window and good electrochemical performance is manufactured, that fulfills the requirements of wearable electronics. First, iron oxide (Fe2O3) nanosheets are directly grown in situ on the surface of stainless steel yarn (SSY) by an acid corrosion and self‐oxidation process, and then a polypyrrole (PPy) coating is covered on the surface of Fe2O3 nanosheets via chemical oxide method to obtain the thread‐like PPy@Fe2O3@SSY composite electrode. The electrode achieves a wide potential range of −1.0–0.8 V (versus Ag/AgCl) and a high areal specific capacitance of 667.8 mF cm−2 with outstanding galvanostatic charge/discharge cycling stability of 87.5% capacitance retention after 10 000 cycles in 1 m lithium sulfate (Li2SO4) aqueous solution. The symmetric TSC based on the PPy@Fe2O3@SSY electrode and carboxymethyl cellulose sodium salt/Li2SO4 gel electrolyte exhibits a wide operating voltage window of 1.8 V, and its maximum energy density can reach 39.3 μWh cm−2. Additionally, the TSC demonstrates excellent electrochemical performance under various bending states and a bending cycling test. The preparation method and raw materials are low‐cost and scalable, and the overall performance of the TSC is excellent, which makes this device a promising energy storage device for wearable electronics. Stainless steel yarn (SSY) is used as a support, iron source and current collect at the same time to obtain a binder‐free PPy@Fe2O3@SSY electrode without the use of other ferrous chemicals. Then a symmetric thread‐like supercapacitor (TSC) based on the PPy@Fe2O3@SSY electrode with high operating voltage window of 1.8 V in neutral aqueous electrolyte and excellent electrochemical performance is fabricated.