Facile synthesis of iron-doped hollow urchin-like MnO₂ for supercapacitors

Hollow urchin-like iron-doped manganese dioxide (Fe–MnO₂) architectures were successfully prepared without any template or surfactant via a facile one-step hydrothermal route. Hollow urchin-like Fe–MnO₂ architectures were made up of interleaving nanosheets, resulting in porous structures and high specific surface area. The formation mechanism of hollow urchin-like Fe–MnO₂ architectures was proposed based on the Ostwald ripening process. When employed as supercapacitor electrode material, hollow urchin-like Fe–MnO₂ delivered a specific capacitance of 203.3 F g⁻¹ at 250 mA g⁻¹ as well as a good capacity retention of 88.1% after 1000 cycles at 5 A g⁻¹. Coupled with activated carbon (AC) negative electrode, Fe–MnO₂//AC asymmetric supercapacitor (Fe–MnO₂//AC ASC) achieved an energy density of 20.2 Wh kg⁻¹ at a power density of 225 W kg⁻¹ and 83.8% capacity retention after 1000 cycles at 3 A g⁻¹, suggesting its potential applications for energy storage.