CNT-rGO-wrapped FeCo₂O₄ for asymmetric supercapacitor with enhanced power density and rate capability

Supercapacitors employing transition metal oxide electrodes exhibit larger specific capacities and energy densities. Performance enhancement of the transition metal oxide electrodes can be achieved by incorporation of carbonaceous materials, to form composite electrode. However, incorporation of carbonaceous materials during the synthesis process can alter the morphological properties of the transition metal oxides. Iron cobaltite (FeCo₂O₄) (FCO) nanosheets exhibit large specific surface area and pore volume, which enhances the loading and diffusion of ions within the electrode. Herein, we designed composite electrodes made up of FCO, reduced graphene oxide (rGO), and functionalized multi-walled carbon nanotubes (f-MWCNTs) while retaining the high specific surface area of the FCO nanosheets. At 3 A g⁻¹, the composite electrode exhibits specific capacity, C_s of 1091 C g⁻¹ as compared with 555 C g⁻¹ of the pristine FCO. Used in an asymmetric supercapacitor, the composite electrode demonstrates maximum energy density of 34 Wh kg⁻¹, maximum power density of 4479 W kg⁻¹, and 92% capacity retention after 5000 cycles. In contrast, the pristine FCO retains only 70% of its capacity after 3000 cycles.