Interlinked multiphase Fe-doped MnO2 nanostructures: a novel design for enhanced pseudocapacitive performance.

Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g(-1) even under a high mass loading (∼5 mg cm(-2)). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm(-3)) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g(-1). The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. This rational multiphase composite strategy provides a promising idea for materials scientists to design and prepare scalable electrode materials for energy storage devices.