Zn doping induces rich oxygen vacancies in δ-MnO2 flower-like nanostructures for impressive energy density coin cell supercapacitor

In this work, Zn-doped δ-MnO2 (ZnMO) flower-like nanostructures on carbon fibers are synthesized by one-pot hydrothermal method. It is found that insertion of Zn ions induces oxygen vacancy defects, increase in active sites and conductivity of δ-MnO2 (MO) structure. These features making ZnMO structure an excellent candidate for the fabrication of electrode material for supercapacitors. It has been revealed that ZnMO@CC electrode delivered an enhanced specific capacitance of 667 F g−1 at a current density of 1 A g−1 as compared to the pristine δ-MnO2 and previously reported nanostructures. The developed asymmetric coin cell supercapacitor (ZnMO//AC) obtained a specific capacitance of 116 F g−1 at 1 A g−1 and achieved an outstanding energy density of 71.5 Wh kg−1 at a power density of 1067.1 W kg−1. Moreover, the device retains its initial capacitance of 92 % after 8000 cycles at 8 A g−1. These results suggest that ZnMO could be an emerging electrode material for the fabrication of high-performance supercapacitors for practical applications. This research hunts for new visions for the preparation of MnO2-based material by doping strategy for energy storage applications, especially supercapacitor.