Advanced three-dimensional hierarchical porousα-MnO₂nanowires network toward enhanced supercapacitive performance

Hierarchicalα-MnO₂nanowires with oxygen vacancies grown on carbon fiber have been synthesized by a simple hydrothermal method with the assistance of Ti⁴⁺ions. Ti⁴⁺ions play an important role in controlling the morphology and crystalline structure of MnO₂. The morphology and structure of the as-synthesized MnO₂could be tuned fromδ-MnO₂nanosheets to hierarchicalα-MnO₂nanowires with the help of Ti⁴⁺ions. Based on its fascinating properties, such as many oxygen vacancies, high specific surface area and the interconnected porous structure, theα-MnO₂electrode delivers a high specific capacitance of 472 F g^-1at a current density of 1 A g^-1and the rate capability of 57.6% (from 1 to 16 A g^-1). The assembled symmetric supercapacitor based onα-MnO₂electrode exhibits remarkable performance with a high energy density of 44.5 Wh kg^-1at a power density of 2.0 kW kg^-1and good cyclic stability (92.6% after 10 000 cycles). This work will provide a reference for exploring and designing high-performance MnO₂materials.