Iron oxide@CoFe-LDH nanocomposites for highly stable aqueous hybrid supercapacitors†

Abstract

CoFe-LDH (layered double hydroxide) nanomaterials are widely explored as battery-type electrode materials owing to their excellent redox activity, layered structure, and fast ion diffusion. However, their practical application is often hindered by poor cyclic stability. The nanocomposite of CoFe-LDH with iron oxide has great potential to overcome this limitation. The layered structure of CoFe-LDH facilitates a fast ion diffusion and realizes synergistic activities of multiple metal elements, while iron oxide prevents the self-restacking and aggregation of CoFe-LDH layers, which ultimately enhance their structural stability and electrochemical performance. In this work, we prepared an Fe₁₆O₂₀/CoFe-LDH (FO@CoFe-LDH) nanocomposite via a single-step hydrothermal method. As composition tuning was a major concern to regulate the electrochemical performance, two samples with different compositions were prepared by tuning the mole ratios of Co and Fe. Electrochemical investigations of FO@CoFe-LDH1 (3 : 1 ratio of Co : Fe) demonstrated a specific capacity of 84 C g⁻¹ at 1 A g⁻¹, while FO@CoFe-LDH2 (3 : 2 ratio of Co : Fe) was limited to 25 C g⁻¹ at 1 A g⁻¹ in a 6 M KOH electrolyte solution. Furthermore, an aqueous hybrid supercapacitor (AHS) fabricated using FO@CoFe-LDH1 as the positive electrode and activated carbon (AC) as the negative electrode exhibited remarkable cyclic stability, retaining 99.9% after 4000 cycles. This study demonstrates the potential of FO@CoFe-LDH1 nanocomposites as battery-type electrodes for AHS devices, paving the way for durable energy storage devices.