Graphene decorated iron oxide negative electrodes with high capacity, excellent rate performance, and wide working voltage for aqueous battery-supercapacitor hybrid devices

Battery-supercapacitor hybrid (BSH) devices are novel energy storage components for configuration engineering, which are receiving increasing attention in recent years. Fe2O3-based materials with wide potential windows are promising negative electrodes in aqueous electrolytes. However, Fe2O3-based negative electrodes exhibiting more than 90% rate capability at high current density have been rarely reported. Such high rate capability can further promote the application of BSH device for high power storage. In this study, Fe2O3/reduced graphene oxide (rGO) composites with potential windows ranging from −0.15 to −1.2 V and unprecedented rate capability of 91.08% are prepared by fine regulation of the component ratios. The electrode tested in 6 M KOH electrolyte provides an excellent specific capacity of 413 C g−1. The electrode shows merits in capacity, rate capability and potential window simultaneously. Also, bulk charge storage leads to high specific capacity of perovskite. These features can raise the energy density of BSH device to 77.5 W h kg−1 by properly matching the modified La0.85Sr0.15MnO3@NiCo2O4 perovskite composite as positive electrode (826 C g−1) and Fe2O3/rGO as negative electrode. The device also exhibits excellent power density (54,000 W kg−1). In sum, the proposed device with superior electrochemical behavior can further promote the practical applications of perovskite-based or Fe2O3-based BSH devices. [Display omitted] •The sample had merits in capacity, rate capability and potential window concurrently.•The Fe2O3@rGO negative electrode had high rate capability of 91.08% at 20 A g−1.•The La0.85Sr0.15MnO3@NiCo2O4//Fe2O3/rGO device was assembled firstly.•The device performed high energy density of 77.5 W h kg−1 at 900 W kg−1.