Polyvinylpyrrolidone-Functionalized NiCo₂O₄ Electrodes for Advanced Asymmetric Supercapacitor Application

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-performance supercapacitive energy storage requires advanced electrode architectures with tailored morphology and redox synergy.
• Binder-free electrodes synthesized directly on conductive substrates are crucial for minimizing interfacial resistance and maximizing electrochemical performance.

Purpose of the Study:

• To synthesize binder-free NiCo2O4 nanostructured electrodes on nickel foam using a PVP-assisted hydrothermal method.
• To engineer hierarchical flower-like nanosheet morphology by modulating PVP concentration for enhanced electrochemical properties.
• To evaluate the performance of the optimized electrode and an asymmetric supercapacitor device for flexible energy storage applications.

Main Methods:

• Hydrothermal synthesis of NiCo2O4 nanostructures on nickel foam substrates with varying polyvinylpyrrolidone (PVP) concentrations (0.5-2 wt%).
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Fabrication and testing of an asymmetric pouch-type supercapacitor device using the optimized NiCo-P1 electrode and activated carbon (AC).

Main Results:

• The NiCo-P1 sample (1 wt% PVP) exhibited an optimized hierarchical flower-like nanosheet structure with superior surface area and ion accessibility.
• NiCo-P1 delivered an exceptional areal capacitance of 36.5 F/cm² at 10 mA/cm² and retained 80.97% after 15,000 cycles.
• The asymmetric NiCo-P1//AC supercapacitor achieved an areal capacitance of 187 mF/cm², energy density of 0.058 mWh/cm², and 78.78% retention after 5000 cycles.

Conclusions:

• The surfactant-directed design using PVP is effective in creating high-performance NiCo2O4 electrodes for supercapacitors.
• The synergistic effects of mixed-valence Ni and Co, engineered morphology, and low resistance contribute to the superior electrochemical performance.
• This study highlights a promising strategy for developing cost-effective, high-performance electrodes for next-generation flexible energy storage technologies.