Electrical and electrochemical characterization of FeCo₂O₄ nanoflakes for flexible supercapacitor applications

Iron-substituted cobalt oxide spinel in the form of FeCo₂O₄ nanoflakes was synthesized by using a wet-chemical co-precipitation process. The presence of a metal-oxide bond was confirmed using FTIR spectroscopic analysis. A study of the phase and exterior morphology of FeCo₂O₄ nanoflakes confirms the formation of single-phase nano-sized grains. Electrical property analysis shows negative temperature coefficient (NTC) behaviour with high electrical conductivity at elevated temperatures. This fact was also supported by a decrease in the thermal activation energy at higher temperatures. The dominance of small grains and decreasing relaxation time are noteworthy aspects in determining the conduction mechanism in lower and higher temperatures, respectively. The highest specific capacitance was computed to be between 1048.07 and 1690.14 F g⁻¹ for flexible and stiff copper current collectors, endorsing the usability of FeCo₂O₄ nanoflakes as a superior electrode material. The energy and power densities were estimated to be 47.32 Wh/kg and 759.85 W/kg, respectively, substantiating the use of prepared electrode material for both flexible and solid-state energy storage devices. The decrease in the diameter of Cole–Cole plot and almost leaner characteristics observed in the electrochemical impedance spectrum establishes the NTC trend and low internal resistance, respectively, of FeCo₂O₄ nanoflakes.