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

Transition metal oxides have attracted extensive research interest for supercapacitors due to efficient ion accessibility of nanostructures. Here, hierarchically hollow α-K0.2MnTi0.07O0.8 nanotubes with high K content are prepared via a self-sacrificial template method. The electrochemical performance of α-K0.2MnTi0.07O0.8 nanotubes is significantly improved when beneficial K+ is intercalated into a considerably ordered α-MnO2 phase with exchangeable Mn–K slabs by a K-pre-reserved reaction. Significantly, the α-K0.2MnTi0.07O0.8 nanotubes activated in a K2SO4 electrolyte exhibit highly capable capacitance behavior with high specific capacitance (334.5 F g–1 at 1 A g–1) and superior cycling stability (88% capacitance retention of the initial after 60,000 cycles). The well-designed α-K0.2MnTi0.07O0.8-based supercapacitor device exhibits an energy density of 25.16 Wh kg–1 at 1600 W kg–1. The morphological electrode-structured designer could be a promising attempt for applications in energy-related fields and even beyond power and storage sources.