Defective core–shell NiCo2S4/MnO2 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 NiCo 2 S 4 /MnO 2 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 2 is well coated on the core-NiCo 2 S 4 . 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 NiCo 2 S 4 /MnO 2 electrode of reduction for 60 min (NiCo 2 S 4 /MnO 2 -60) are effectively adjusted by introducing oxygen vacancies. Impressively, the NiCo 2 S 4 /MnO 2 -60 electrode delivers substantially appreciable areal capacity of 2.13 mAh·cm −2 couple with superior rate capability. The as-prepared high-performance electrode material can assemble into solid-state hybrid supercapacitor . The fabricated NiCo 2 S 4 /MnO 2 -60//AC device exhibits an exceptional energy density of 43.16 Wh·kg −1 at a power density of 384.21 W·kg −1 and satisfactory cyclic stability of 92.1 % at current density of 10 mA·cm −2 after 10,000 cycles. In general, the work demonstrates the significance of NiCo 2 S 4 /MnO 2 -60 as a highly redox active electrode material for future practical application in supercapacitors .