Defective core-shell NiCoS/MnO nanocomposites for high performance solid-state hybrid supercapacitors.

The roles of oxygen vacancies to enhance the electrochemical performance were not clearly explained in comprehensive research. Herein, the vertically oriented NiCoS/MnO core-shell nanocomposites are in situ grown on the nickel foam (NF) surface and activated by oxygen vacancy engineering via a chemical reduction method. The scanning electron microscope (SEM) and transmission electron microscope (TEM) results show the shell-MnO is well coated on the core-NiCoS. The hierarchical core-shell nanostructures synergistically increase conductivity and provide rich faradaic redox chemical reactions. Moreover, the density functional theory (DFT) calculations further indicate that the electronic properties and structure properties in NiCoS/MnO electrode of reduction for 60 min (NiCoS/MnO-60) are effectively adjusted by introducing oxygen vacancies. Impressively, the NiCoS/MnO-60 electrode delivers substantially appreciable areal capacity of 2.13 mAh·cm couple with superior rate capability. The as-prepared high-performance electrode material can assemble into solid-state hybrid supercapacitor. The fabricated NiCoS/MnO-60//AC device exhibits an exceptional energy density of 43.16 Wh·kg at a power density of 384.21 W·kg and satisfactory cyclic stability of 92.1 % at current density of 10 mA·cm after 10,000 cycles. In general, the work demonstrates the significance of NiCoS/MnO-60 as a highly redox active electrode material for future practical application in supercapacitors.