Hierarchical ZnMn2O4@ZnMn2O4 nanoflower architectures grown on Ni foam as promising electrodes for high-performance supercapacitors.

Supercapacitors have been promising electrochemical energy storage systems due to their long cycle life, rapid charge-discharge, and high-power density. However, the performance of supercapacitor devices mainly depends on the electrode material structure and morphology. In this regard, the present study reports a new advanced electrode material, the ZnMn2O4@ZnMn2O4 architecture, successfully grown on a nickel foam substrate via a facile two-step hydrothermal route without binders or additives. Surface morphology results reveal that the ZnMn2O4@ZnMn2O4 architecture exhibits a flower-like morphology comprising interconnected nanoplatelet structures. Electrochemical results indicate that the hierarchical ZnMn2O4@ZnMn2O4 architecture electrode material exhibits pseudocapacitive behavior with improved charge-transfer kinetics and enhanced ion diffusion. The sequentially grown ZnMn2O4 structured electrode exhibits a high specific capacitance of 230.34 F g-1 at 1 mA cm-2, nearly double that of the bare ZnMn2O4 electrode (121.63 F g-1). Moreover, the ZnMn2O4@ZnMn2O4 architecture electrode delivers a superior cycling stability of 88.85% over 5000 cycles compared to that of the bare ZnMn2O4 electrode (85.96%). Therefore, these findings conclude that the hierarchical architecture with a higher active-material loading of ZnMn2O4@ZnMn2O4 is a promising electrode material for high-performance supercapacitor applications.