High-Temperature Tolerant Flexible Supercapacitors with Redox-Active Water-in-Salt Hydrogel Electrolytes

作者：Chong Peng, Na Wang, Xinyi Huang, Mingwei Zhao, Siyu Yu · 发表于：ACS Sustainable Chemistry & Engineering · 年份：2025 · DOI：10.1021/acssuschemeng.5c05460 · 被引用次数：3 · 研究领域：Supercapacitor Materials and Fabrication、Aerogels and thermal insulation、Advanced battery technologies research

High-temperature-tolerant flexible supercapacitors are essential for powering emerging wearable and portable devices operating under harsh environmental conditions. Conventional hydrogel electrolytes exhibit excellent ionic conductivity, flexibility, and biocompatibility; however, their practical application is hindered by water evaporation at elevated temperatures and a narrow electrochemical window limited by the water decomposition voltage (1.23 V). In this work, we present a novel heat-resistant and redox-active hydrogel electrolyte containing a ZnCl 2 water-in-salt solution and a redox-active additive of (NH 4 ) 2 Fe(SO 4 ) 2 . The strong coordination between Zn 2+ ions and water molecules effectively suppresses water activity, thereby enhancing the thermal stability and expanding the electrochemical window. Furthermore, the incorporation of (NH 4 ) 2 Fe(SO 4 ) 2 contributes to both faradaic charge storage through Fe 2+ /Fe 3+ redox reactions and improved thermal stability via enhanced water coordination. When paired with KOH-activated carbon nanofiber electrodes, a redox electrolyte enhanced flexible supercapacitor has been constructed. The device delivers a wide working voltage of 2.0 V, a high energy density of 23.2 Wh kg –1, and stable operation across a broad temperature range from 0 to 100 °C. This work offers a promising strategy for developing high-performance, thermally stable energy storage devices suitable for next-generation flexible electronics.