Vanadium-doped nanoporous structure on stainless steel substrate for high-performance flexible supercapacitor

Abstract

Ferric oxide nanopores on stainless steel substrates offer a promising cathode structure for flexible supercapacitors, but their capacitance and cycling stability remain insufficient for practical use. In this study, we develop vanadium-doped nanoporous structures on stainless steel foil using a simple, cost-effective in-situ anodic oxidation method, optimizing the doping concentration. The resulting electrode exhibits a specific capacitance of 320.9 mF cm⁻2 at a current density of 1 mA cm⁻2, a 3.17-fold increase over the undoped counterpart, with 88.4 % capacitance retention after 8000 cycles. To demonstrate practical viability, we assemble a flexible hybrid supercapacitor by pairing the vanadium-doped cathode with a typical activated carbon-coated carbon cloth anode. The device exhibits a wide operating potential window of 1.8 V, a high energy density of 58.83 mWh·cm⁻³, and a power density of 0.5 W cm⁻³, alongside robust bending tolerance. The enhanced performance is attributed to an increased number of redox reaction sites and reduced internal resistance, as confirmed through both experimental and theoretical analysis. These findings highlight the potential of vanadium-doped nanoporous structures for use in high-performance, flexible, and cost-effective supercapacitors.