Homogeneous formation of MnO@V₂O₅ composites for asymmetrical supercapacitors with high energy density and long cycle...

Strategies to achieve high-performance supercapacitors involve designing composite electrode materials that have fast charge transport and a high number of redox-active sites. A MnO@V₂O₅ composite was effectively prepared and tested in this study as a promising electrode material in aqueous asymmetrical supercapacitors. The presence of crystalline MnO and V₂O₅ phases, hierarchical architecture, and the homogeneous hybrid of Mn, V and O throughout the composite were all validated by structural and morphological characterization. Capitalizing on the synergistic nature of the MnO and V₂O₅ interaction, the composite demonstrated much better electrochemical behaviour in 3 M KOH electrolyte, with respect to improved redox activity, a faster reaction rate as well as the charge-transfer properties, in comparison to the constituent oxides. This MnO@V₂O₅ composite electrode provided a high specific capacity of 421.8 C g^-1 at 1 A g^-1 and performed well at high scan rates. The kinetic analysis revealed that there was a mixture of diffusion-controlled and capacitive charge storage and the capacitive contribution was higher in the composite. In addition, an asymmetric supercapacitor that operates on MnO@V₂O₅//AC demonstrated stable cycling to up to 1.8 V, a specific capacitance of 117 F g^-1 at 1 A g^-1, a maximum energy density of 53 Wh kg^-1 at a power density of 899 W kg^-1, and excellent cycling stability with a retained capacity of 91% after 16 000 charge discharge cycles. These results indicate that the MnO@V₂O₅ composite is a promising material for the next generation supercapacitors with high energy and durability.