Performance Enhancement Of Mno₂-Based Electrodes In Aqueous Supercapacitors Using Redox Additives
Keywords:
MnO₂ electrodes, redox additives, aqueous supercapacitors, electrochemical performance, energy density, cyclic voltammetry, galvanostatic charge–discharge, impedance spectroscopyAbstract
The study examines a holistic approach in improving the performance of aqueous super capacitors by taking advantage of the synergistic working of MnO2 based electrodes and redox-active electrolyte additives. Manganese dioxide (MnO2 ) has been selected due to its high theoretical capacitance, low cost, but may have low electrical conductivity and low rate ability. An approach to suppress these shortcomings is the synthesis of nanostructured MnO2 by hydrothermal protocols to enhance the surface area and accessibility of the ion, and the incorporation of these protocols into aqueous electrolyte solutions enriched with redox-active mediators such as potassium iodide (KI), potassium ferricyanide (K3[Fe(CN)6), and potassium bromide (KBr).
A comparative electrochemical analysis was done by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in neutral and alkaline electrolytic conditions. It was shown that the redox additives significantly enhanced the specific capacitance, the energy density, the power density, and the long-term cycling stability of the MnO2-based super capacitors. Specifically, the addition of 0.2 M K 3 [Fe(CN) 6 ] to a 1 M Na 2 SO 4 electrolyte resulted in an impressive increase in specific capacitance of 332.8 F/g (pristine) to 1590 F/g whereas 0.05 M KI in 3 M KOH was able to achieve a high energy density of 90 Wh/kg with appreciably stable cycling behavior of over 91% retention on 10,000 cycles.
The rapid reversible redox reactions of the mediators, the charge shuttles, to the electrode kinetics and low resistance to charge transfer were credited to the enhancement mechanisms. Structural and morphological analyses using SEM and XRD confirmed the successful formation of nanostructured α-MnO₂ with favorable electrochemical surface characteristics. The electrochemical behavior was further supported by Nyquist plots showing reduced equivalent series resistance (ESR) and improved ion diffusion dynamics.
This study establishes that carefully selected redox-active additives, when combined with engineered MnO₂ electrode architectures, can significantly enhance the efficiency and durability of aqueous supercapacitor systems. The proposed strategy provides a cost-effective, scalable route toward high-performance energy storage devices and lays the groundwork for future research in hybrid redox-electrode systems for next-generation supercapacitors.
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