Symmetrical supercapcitors with α-MnO₂ nanorods/carbon nanofiber (CNF) composite as electrode material

α-MnO₂ nanorods have been grown on the surface of CNF for enhancing the electrical conductivity of MnO₂. α-MnO₂/CNF (0-5 wt%) nanocomposites were synthesized using a co-precipitation method. The XRD results confirm the formation of a single phase α-MnO₂ and SEM/TEM images reveal the formation of α-MnO₂ nanorods. While α-MnO₂/CNF(1.25 wt%) exhibits the largest surface area (381 m²/g) and only a slight increase in the electrical conductivity (0.05 S/cm), α -MnO₂/CNF(5 wt%) shows the least surface area (131 m²/g) but an order of magnitude higher electrical conductivity (0.67 S/cm), compared to pure α-MnO₂ nanorods. C-V measurements show improved performance in all α-MnO₂/CNF supercapacitors compared to that of pure α-MnO₂. Ragone plot shows that although α-MnO₂/CNF(1.25 wt%) exhibits the highest specific capacitance (313 F/g at 1 A/g) and hence the highest energy density of 32.8 Wh/kg, it has a lower power density of 2720 W/kg. On the other hand, α-MnO₂/CNF(5 wt%) shows the least energy density of 7.9 Wh/kg, but has a higher power density of 4640 W/kg. Results demonstrate that one can optimize both energy and power densities by controlling the amount of CNF in the nanocomposites.