Polyvinylpyrrolidone-Functionalized NiCo2O4 Electrodes for Advanced Asymmetric Supercapacitor Application
Rutuja U. Amate, Mrunal Bhosale, Pritam J. Morankar, Aviraj M. Teli, Chan‐Wook Jeon
Abstract
Designing advanced electrode architectures with tailored morphology and redox synergy is essential for achieving high-performance supercapacitive energy storage. In this study, a PVP-assisted hydrothermal approach was employed to synthesize binder-free NiCo2O4 nanostructured electrodes directly on nickel foam substrates. By modulating the PVP concentration (0.5–2 wt%), hierarchical flower-like nanosheets were engineered, with the NiCo-P1 sample (1 wt% PVP) exhibiting an optimized structure, superior electroactive surface area, and enhanced ion accessibility. Comprehensive electrochemical analysis revealed that NiCo-P1 delivered an outstanding areal capacitance of 36.5 F/cm2 at 10 mA/cm2, along with excellent cycling stability over 15,000 cycles with 80.97% retention. Kinetic studies confirmed dominant diffusion-controlled redox behavior with high OH− diffusion coefficients and minimal polarization. An asymmetric pouch-type supercapacitor device (NiCo-P1//AC) exhibited a wide operating window of 1.5 V, achieving a remarkable areal capacitance of 187 mF/cm2, energy density of 0.058 mWh/cm2, and capacitive retention of 78.78% after 5000 cycles. The superior performance is attributed to the synergistic integration of mixed-valence Ni and Co species, engineered nanosheet morphology, and low interfacial resistance. This work underscores the significance of surfactant-directed design in advancing cost-effective, high-performance electrodes for next-generation flexible energy storage technologies.