Construction of IrO2@Mn3O4 core-shell heterostructured nanocomposites for high performance symmetric supercapacitor device

Highlights: • Thin films of IrO₂ nanofibers laminated with Mn₃O₄ nanoflakes are synthesized. • Uniform lamination of Mn₃O₄ nanoflakes over IrO₂ nanofibers is obtained. • The charge storage kinetics of IrO₂@Mn₃O₄ electrodes is studied in detail. • The specific capacitance of 1027 F/g at 1 mA/cm² with 91% cyclic stability is achieved. • The fabricated gel-based symmetric device shows an energy density of 81 Wh/kg at 714 W/kg. -- Abstract: In the present work, we have designed and synthesized nanocomposite of IrO₂@Mn₃O₄ with two-step simple and scalable chemical routes. In this route, nanofibers of IrO₂ were synthesized by a single nozzle electrospinning technique onto which Mn₃O₄ was overlaid by a simple SILAR route. The ratio of Mn₃O₄ and IrO₂ was varied by varying the SILAR cycles onto electrospun IrO₂ thin film as 20, 40, 60, and 80 cycles. The structural, morphological, and energy storage performance of IrO₂@Mn₃O₄ composite electrodes were investigated. A 2 V kinetic potential with a rectangular-shaped cyclic voltammogram was observed for the IrO₂@Mn₃O₄ electrodes. Moreover, the specific capacitance of 1027 F/g at 1 mA/cm² was observed for the optimized electrode which is superior as compared with other electrodes. The optimized electrode showed better current and voltage than the individual compounds which might be due to the synergic effect of IrO₂ and Mn₃O₄. Finally, a PVA-LiClO₄ gel electrolyte-based solid-state IrO₂@Mn₃O₄//IrO₂@Mn₃O₄ symmetric device was fabricated. The symmetric device possessed an energy density of 81 Wh/kg with a power delivery of 714 W/kg which was capable to light up a green LED. Hence, the 2D transition metal oxides laminated on 1D metal oxides with high conductivity can be promising electrodes for future research.