Surface-functionalized Fe2O3 nanowire arrays with enhanced pseudocapacitive performance as novel anode materials for high-energy-density fiber-shaped asymmetric supercapacitors

Abstract Fiber-shaped asymmetric supercapacitors (FASCs) have potential applications in next-generation wearable and portable electronics due to their high power density, remarkable flexibility, fast charge-discharge capability, long cycle life and light weight. However, low specific capacitance and energy density hinder their practical applications. To obtain anode materials with high conductivity and high specific capacity, we first synthesize Fe2O3 nanowire arrays (NWAs) on carbon nanotube fibers as negative electrodes and then obtain FeS2 and FeP NWAs negative electrodes by sulfuration and phosphorization, respectively. The transformation processes effectively enhance the desirable properties of the electrode materials, improving the areal capacitance from 292 mF cm−2 to 833 mF cm−2 (sulfuration) and 1135 mF cm−2 (phosphorization) at a current density of 1 mA cm−2, demonstrating a significant improvement compared to Fe2O3 NWAs and, importantly, that phosphorization produces better results than sulfuration. Furthermore, the fabricated FASC exhibits outstanding mechanical flexibility and weavability and thus has great potential in for practical application in novel wearable and portable supercapacitors, which are expected to be the next generation of flexible energy-storage devices.