Construction of δ-MnO2/Mn2O3 flower sphere composite with two-dimensional hierarchical nanosheets as supercapacitor electrode with enhanced performance

Mn 2 O 3 is and has received widespread attention in fields such as catalysis and energy storage. However, its poor conductivity limits its application as an electrode material for supercapacitors. Here, flower-like spheroidal δ-MnO 2 /Mn 2 O 3 composites composed of two-dimensional (2D) hierarchical nanosheets were prepared by the template method and a simple hydrothermal process. The growth process and electrochemical properties of δ-MnO 2 /Mn 2 O 3 composites were investigated by adjusting the concentration of KMnO 4 in the hydrothermal process. Since the introduction of δ-MnO 2 brings more pseudocapacitance to the composite, the synergistic effect between MnO 2 and Mn 2 O 3 reduces the interfacial resistance, and the unique nanosheet structure increases its specific surface area, which alleviates the volume expansion during the cycling, the δ-MnO 2 /Mn 2 O 3 composite electrode exhibits high specific capacitance (182 F g −1 at 0.5 A g −1 ), fast rate performance (74.2% capacitance retention at 5 A g −1 ), and excellent cyclic stability (90.1% capacitance retention after 5000 cycles at 5 A g −1 ). Symmetric supercapacitors assembled with δ-MnO 2 /Mn 2 O 3 electrodes also exhibit a high energy density of 9.1 Wh kg −1 . δ-MnO 2 /Mn 2 O 3 composites have greater application prospects in energy storage, and are expected to achieve further applications in lithium/sodium ion batteries, zinc ion batteries and other fields.