K+-Pre-Intercalated alpha-K0.2MnTi0.07O0.8 Hollow Nanotubes for High-Performance Na+ Supercapacitors

Transition metal oxides have attractedextensive research interestfor supercapacitors due to efficient ion accessibility of nanostructures.Here, hierarchically hollow alpha-K0.2MnTi0.07O0.8 nanotubes with high K content are prepared via aself-sacrificial template method. The electrochemical performanceof alpha-K0.2MnTi0.07O0.8 nanotubesis significantly improved when beneficial K+ is intercalatedinto a considerably ordered alpha-MnO2 phase with exchangeableMn-K slabs by a K-pre-reserved reaction. Significantly, the alpha-K0.2MnTi0.07O0.8 nanotubesactivated in a K2SO4 electrolyte exhibit highlycapable capacitance behavior with high specific capacitance (334.5F g(-1) at 1 A g(-1)) and superiorcycling stability (88% capacitance retention of the initial after60,000 cycles). The well-designed alpha-K0.2MnTi0.07O0.8-based supercapacitor device exhibits anenergy density of 25.16 Wh kg(-1) at 1600 W kg(-1). The morphological electrode-structured designercould be a promising attempt for applications in energy-related fieldsand even beyond power and storage sources.