Solution-combustion synthesis of AgCo3O4/FeMn-O multiphase composite for high-performance asymmetric supercapacitor

A multiphase composite system AgCo3O4/FeMn-O was synthesized using an easy and low-cost solution combustion method for supercapacitor application. The multiphase composite system consisting of Co3O4, alpha-MnO2, and Mn5O8 was identified by X-ray diffraction analysis. The phases were observed as settled on each other in the form of large spherical and hair-like formations in morphological images obtained from scanning electron microscopy. UV-VIS spectroscopy supported the results of variation of band gap energies of Co3O4, alpha-MnO2, and Mn5O8 due to Ag and Fe. Based on Raman spectroscopy, characteristic modes of Co3O4, alpha-MnO2, and Mn5O8 were observed. In electrochemical analysis, the cyclic voltammetry (CV) confirmed the intercalation typepseudocapacitive nature of the prepared composites. Galvanostatic charge-discharge (GCD) analysis showed the highest specific capacitance of 904 F/g obtained from one of the composites at 1 A/g current density. The supercapacitor device was fabricated and showed remarkable cyclic stability of 89 % even after 5000 GCD cycles along with 11.5 Wh/kg energy density and 522 W/kg power density. The good electrochemical performance was attributed to the multiple redox reactions occurred in the bulk of electrode material. Hence, the solution combustion method provides an easy and cost-effective approach to synthesize metal-oxide composites for super- capacitor applications.