V2O5-MnO2 nanocomposites as an efficient electrode material for high-performance aqueous supercapacitors

Redox-active supercapacitors are very interesting due to their high energy density (>25 Wh kg⁻¹ at device level) and redox charge storage mechanism. In this work, V₂O₅-MnO₂ nanocomposites are synthesized by a scalable hydrothermal approach. MnO₂ in V₂O₅ provides better structural stability with reasonable electrochemical performance, in which V₂O₅ enhances the cyclic stability and rate capabilities. The V₂O₅-MnO₂ -based electrodes deliver a specific capacitance of 266 F g⁻¹ at 0.5 A g⁻¹ and are stable up to 6500 cycles with 97 % capacitance retention at 5 A g⁻¹. The kinetic study depicts that composite electrodes have a 64 % diffusive and 36 % capacitive charge storage contribution to the overall charge storage at 1 mV s⁻¹. In symmetric full cells, the composite materials show a wide active potential window of 2.5 V and retain 83 % capacitance after 10000 continuous GCD cycles at an applied current density of 2 A g⁻¹. The promising charge storage performance is due to a suitable conducting matrix and the effective coating of MnO₂ nanoparticles over the unique V₂O₅ niddle shape (two-dimensional) micro-rods.