High-performance adjustable manganese oxides hybrid nanostructure for supercapacitors

Abstract

Manganese oxides based supercapacitors have shown great potential in portable electronics. However, the limited energy density of MnO2-based electrodes is still a developmental bottleneck that restricts their practical applications. In this work, we use hydrothermal method to grow highly regular MnO2 nanoclusters on oxidized carbon fiber as sponge layer, in which Mn3O4 nanospheres are expanded in MnO2 by hydrothermal method again, forming a hierarchical core-shell nanostructure. The activatable nanoparticles undergo a phase change by cycling protocol, providing high accessible surface area and more exposed active sites. The resulting MnO2/Mn3O4 electrode exhibits an excellent performance such as a superior specific capacitance of 1709 F g − 1 at 1 A g − 1 in 1.0 M Na2SO4 aqueous electrolyte, a good electrochemical cycling stability with 91.9% and 71.67% retentions of initial specific capacitance and nearly 100% coulumbic efficiency respectively after 6000 and 20,000 cycles at 10 A g − 1. The assembled asymmetrical ASC displayed a maximum operating voltage of 1.9 V, a high specific capacitance of 198.6 F g − 1 at 0.8 A g − 1 and an exceptional energy density of 234 W h kg−1. These results open up new paths for exploring high-performance manganese oxide-based electrode materials and applying for advanced energy storage devices.