Among energy storage devices, supercapacitors have received considerable attention in recent years owing to their high-power density and extended cycle life. Researchers are currently making efforts to improve energy density using different asymmetric cell configurations, which may provide a wider potential window. Many studies have been conducted on positive electrodes for asymmetric supercapacitor devices; however, studies on negative electrodes have been limited. In this study, iron oxides with different morphologies were synthesized at various deposition temperatures using a simple chemical bath deposition method. A nanosphere-like morphology was obtained for α-Fe2O3. The obtained specific capacitance (Cs) of α-Fe2O3 was 2021 F/g at a current density of 4 A/g. The negative electrode showed an excellent capacitance retention of 96% over 5000 CV cycles. The fabricated asymmetric solid-state supercapacitor device based on α-Fe2O3-NF//Co3O4-NF exhibited a Cs of 155 F/g and an energy density of 21 Wh/kg at 4 A/g.
Keywords: Co3O4; chemical bath deposition; supercapacitor device; α-Fe2O3.