Direct growth of feco₂o₄ nanowire arrays on flexible stainless steel mesh for high-performance asymmetric supercapacitor

Currently, one-dimensional nanostructured binary metal oxides attract a great attention in supercapacitors (SCs) application due to their rapid charge transportation. In this respect, different nanostructures of FeCo₂O₄ are designed by simply tuning the reaction temperature in hydrothermal synthesis. These nanostructures are directly grown on flexible stainless steel mesh and further applied as binder-free electrodes for SCs. The systematic study is carried out to confirm the relation between surface characteristics and electrochemical properties of FeCo₂O₄ thin film. Among different nanostructures, FeCo₂O₄ nanowire arrays exhibit hierarchical mesoporous structure and demonstrate good surface properties including high surface area and appropriate pore volume. As a consequence, relatively high specific capacitance of 1963 F g^{− 1} is obtained for the FeCo₂O₄ nanowire electrode. Further, asymmetric SC is fabricated using nanowired-FeCo₂O₄ and nanoparticulated-MnO₂ thin films as negative and positive electrodes with neutral Na₂SO₄ electrolyte. Impressively, the MnO₂//FeCo₂O₄ cell could be successfully cycled in a wide voltage window of 2.0 V, which can achieve a specific capacitance of 218 F g^{− 1} and energy density of 43 Wh kg^{− 1}. In addition, the SCs exhibit improved capacitance with cycling, which is attributed to opening of micro-pores occurred by frequent ion transport.