Electrochemical performance of asymmetric supercapacitor with binder-free Co_xMn_3-xSe₄ and radish-derived carbon electrodes using K₃[Fe(CN)₆] additive in electrolyte

For the development of high-energy portable electronic devices with long cycling life, herein, we provide an effective strategy of using a small quantity of K₃[Fe(CN)₆] as a redox additive in aqueous KOH solution as the electrolyte, which greatly enhances the energy storage performance of positive electrode via faradaic transitions of redox pair at the electrode–electrolyte interface. Construction of nanoarchitectured Co_xMn_3-xSe₄ arrays on conductive carbon cloth (CC) substrate (CC/CMS arrays) by a facile one-step potentiostatic electrodeposition (chronoamperometry) process and their structural, morphological, and electrochemical characterizations are successfully demonstrated. The allied electron transport mechanism of K₃[Fe(CN)₆] further enhancing the electrochemical performance of optimized CC/CMS array positive electrode in the KOH + K₃[Fe(CN)₆] electrolyte is discussed in detail. Moreover, the novel CC/CMS-based asymmetric supercapacitor (ASC) device is assembled employing biomass-derived radish carbon (Radish-C) negative electrode (i.e., CC/CMS//Radish-C ASC) and separately evaluated in the electrolytes with and without redox additive. In the redox additive KOH + K₃[Fe(CN)₆] electrolyte, the ASC device delivers higher specific capacity (85.7 mAh g⁻¹), energy density (64.3 Wh kg⁻¹), and long-term charge–discharge lifespan (98.8% retention after 10,000 cycles) than that in the pristine KOH electrolyte. The practicality of CC/CMS//Radish-C ASC device in the redox additive electrolyte is also established in this work.