Hierarchical MnO

The strategy of forming hierarchical nanostructures of electroactive materials has shown enhancements in supercapacitor performances. In this study, two hierarchical electrodes are prepared by directly growing MnO2 nanoflowers and SnO2 nanoparticles on rhombohedral LaMnO3 nanostructures using a facile method. An extended potential window of 2 V in a neutral aqueous electrolyte with superior electrochemical characteristics compared to pristine LaMnO3 electrodes is exhibited by these electrodes. Moreover, LaMnO3/MnO2 shows the best performance among the two hierarchical nanostructures. The optimized LaMnO3/MnO2 electrode delivers a high capacity of 426 C g-1 at a current density of 1 A g-1, nearly 4.6 times compared to pristine LaMnO3. This hierarchical electrode, due to the synergistic effect, exhibits appreciable cycling stability, outperforming the electrodes based on pristine MnO2 and LaMnO3. The aqueous symmetric supercapacitor fabricated using this electrode shows a capacity of 64 C g-1 (32 F g-1) at 1 A g-1, with a high energy density of 17.8 Whkg-1 at a constant power density of 2000 W kg-1. Further, the device delivers 89% of its initial capacitance even after 10 000 charge/discharge operations at 10 A g-1. This study presents the possibility of using these hierarchical nanostructures in high-performance aqueous electrolyte supercapacitors (SCs).