Advanced three-dimensional hierarchical porous α-MnO2 nanowires network toward enhanced supercapacitive performance

Abstract Hierarchical α -MnO 2 nanowires with oxygen vacancies grown on carbon fiber have been synthesized by a simple hydrothermal method with the assistance of Ti 4+ ions. Ti 4+ ions play an important role in controlling the morphology and crystalline structure of MnO 2 . The morphology and structure of the as-synthesized MnO 2 could be tuned from δ -MnO 2 nanosheets to hierarchical α -MnO 2 nanowires with the help of Ti 4+ ions. Based on its fascinating properties, such as many oxygen vacancies, high specific surface area and the interconnected porous structure, the α -MnO 2 electrode delivers a high specific capacitance of 472 F g −1 at a current density of 1 A g −1 and the rate capability of 57.6% (from 1 to 16 A g −1 ). The assembled symmetric supercapacitor based on α -MnO 2 electrode exhibits remarkable performance with a high energy density of 44.5 Wh kg −1 at a power density of 2.0 kW kg −1 and good cyclic stability (92.6% after 10 000 cycles). This work will provide a reference for exploring and designing high-performance MnO 2 materials.