Nanoarchitectonics of highly flexible iron-oxide nanoporous electrodes on stainless steel substrate for wearable supercapacitors

Flexible electrode is crucial for wearable electronic devices. To prevent performance degradation due to bending or stretching, the development of highly flexible and durable materials is imperative. Here, we address this challenge by selecting stainless-steel electrodes with excellent stability and flexibility. Through an anodization process on the stainless steel, we created an integrated flexible iron oxide electrode. Chemical vapor deposition and ion implantation were employed to develop concentration-controllable N-doped iron oxide electrodes. Comparative analysis highlights the outstanding performance of ion-implanted electrodes, with a specific capacitance increase of up to 3.01 times (332.375 mF cm−2) at 1 mA cm−2. The N-doped electrode exhibits a capacitance retention of 76.67% after 8000 cycles. Density functional theory calculations reveal N-induced lattice distortion, enhancing ion transport and reducing the bandgap. Leveraging these insights, a flexible asymmetric supercapacitor is assembled, demonstrating exceptional stability and capacitance characteristics across different voltages. The flexibility of the stainless-steel substrate enables the FSC to maintain capacitive performance during bending. This research presents a promising solution for high-performance and stable capacitors in electrochemical energy storage applications.