Core–shell MnO2@Fe2O3 nanospindles as a positive electrode for aqueous supercapacitors

Abstract

Supercapacitors display high power density and long cycling life that are particularly amenable for use in the field of energy storage. However, the cost is a big issue for practical application. Here, cheap Fe₂O₃ spindles from a rich natural resource are used as the positive electrode. Through the twining of MnO₂ nanoflakes via a simple and cost-effective hydrothermal method, a unique structure of a core–shell MnO₂@Fe₂O₃ nanospindle has been prepared. The electrochemical performance of the nanospindles including capacitance and cycling life is markedly improved compared with the pristine Fe₂O₃ spindles. Its specific capacitance is up to 159 F g⁻¹ at a current density of 0.1 A g⁻¹ and especially, the capacitance retention is 97.4% after 5000 cycles in a 0.5 mol L⁻¹ K₂SO₄ neutral aqueous electrolyte. Combined with activated carbon as the negative electrode, the energy density can be up to 43.8 W h kg⁻¹ on the basis of the weights of the two electrodes. These results reveal that the core–shell MnO₂@Fe₂O₃ nanospindles are a promising positive electrode for practical supercapacitors.