Defective core-shell NiCo₂S₄/MnO₂ nanocomposites for high performance solid-state hybrid supercapacitors

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Oxygen vacancies play a crucial role in enhancing electrochemical performance, but their specific impact on NiCo2S4/MnO2 nanocomposites requires further elucidation.
• Developing high-performance electrode materials is essential for advancing energy storage technologies like supercapacitors.

Purpose of the Study:

• To synthesize vertically oriented NiCo2S4/MnO2 core-shell nanocomposites on nickel foam (NF).
• To investigate the effect of oxygen vacancy engineering on the electrochemical properties of NiCo2S4/MnO2.
• To evaluate the performance of these nanocomposites in solid-state hybrid supercapacitors.

Main Methods:

• In situ growth of NiCo2S4/MnO2 core-shell nanostructures on nickel foam.
• Chemical reduction method for oxygen vacancy engineering.
• Characterization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
• Density functional theory (DFT) calculations to understand electronic structure modifications.
• Electrochemical testing of electrode materials and assembled supercapacitor devices.

Main Results:

• Vertically oriented NiCo2S4/MnO2 core-shell nanostructures were successfully synthesized on NF.
• Oxygen vacancy engineering via chemical reduction (60 min) effectively tuned the electronic and structural properties.
• The NiCo2S4/MnO2-60 electrode exhibited a high areal capacity of 2.13 mAh·cm⁻² and superior rate capability.
• The assembled solid-state hybrid supercapacitor (NiCo2S4/MnO2-60//AC) achieved an energy density of 43.16 Wh·kg⁻¹ at a power density of 384.21 W·kg⁻¹.
• The device demonstrated excellent cyclic stability, retaining 92.1% of its capacity after 10,000 cycles.

Conclusions:

• The study highlights the critical role of oxygen vacancies in enhancing the electrochemical performance of NiCo2S4/MnO2 nanocomposites.
• The developed NiCo2S4/MnO2-60 material is a promising candidate for high-performance supercapacitor applications.
• Oxygen vacancy engineering offers a viable strategy for designing advanced electrode materials for energy storage.