Boosting the energy density of iron-cobalt oxide based hybrid supercapacitors by redox-additive electrolytes

Due to the increasing requirement of small electronic devices for high energy output and long-term life-span, hybrid supercapacitor device with ultrahigh energy density and long cycle stability has attracted great attention in recent decades. Herein, we constructed an aqueous FeCo2O4 needle-like array (NLA)/CC-based hybrid supercapacitor using K-3[Fe(CN)(6)] as an electrolyte additive to enhance the pseudocapacitor performance. The extensive charge storage kinetics and the electron transport mechanism of the FeCo2O4-NLA in KOH+K-3[Fe(CN)(6)] electrolyte are discussed. The FeCo2O4-NLA soaked in a 3 M KOH + 0.05 M K-3[Fe(CN)(6)] mixed solution shows high specific capacitance (259.33 mA h g(-1) at 2 A g(-1)), low charge transfer resistance and internal resistance, and long-term cycle stability (over 80.7% of capacitance retention at 10 A g(-1) after 5000 cycles). An aqueous FeCo2O4-NLA//KOH+K-3[Fe(CN)(6)]//AC hybrid supercapacitor device is assembled, which presents increased specific capacitance, long cycle stability (86.4% of the initial capacitance), and ultrahigh energy density (58.8 W h kg(-1) @750.1 W kg(-1)). This work may provide a new approach to obtain high-performance energy storage devices. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A hybrid supercapacitor device using FeCo2O4 needle-like array/CC and K-3[Fe(CN)(6)] was constructed to enhance pseudocapacitor performance. The FeCo2O4-NLA showed high specific capacitance, low resistance, and long-term stability in KOH+K-3[Fe(CN)(6)] electrolyte. An assembled device exhibited increased capacitance, long cycle stability, and ultrahigh energy density.