title: Hierarchical Fe₃O₄@Fe₂O₃ Core-Shell Nanorod Arrays as High-Performance Anodes for Asymmetric Supercapacitors.
abstract: Anode materials with relatively low capacitance remain a great challenge for asymmetric supercapacitors (ASCs) to pursue high energy density. Hematite (α-Fe2O3) has attracted intensive attention as anode material for ASCs, because of its suitable reversible redox reactions in a negative potential window (from 0 V to -1 V vs Ag/AgCl), high theoretical capacitance, rich abundance, and nontoxic features. Nevertheless, the Fe2O3 electrode cannot deliver large volumetric capacitance at a high rate, because of its poor electrical conductivity (∼10(-14) S/cm), resulting in low power density and low energy density. In this work, a hierarchical heterostructure comprising Fe3O4@Fe2O3 core-shell nanorod arrays (NRAs) is presented and investigated as the negative electrode for ASCs. Consequently, the Fe3O4@Fe2O3 electrode exhibits superior supercapacitive performance, compared to the bare Fe2O3 and Fe3O4 NRAs electrodes, demonstrating large volumetric capacitance (up to 1206 F/cm(3) with a mass loading of 1.25 mg/cm(2)), as well as good rate capability and cycling stability. The hybrid electrode design is also adopted to prepare Fe3O4@MnO2 core-shell NRAs as the positive electrode for ASCs. Significantly, the as-assembled 2 V ASC device delivered a high energy density of 0.83 mWh/cm(3) at a power density of 15.6 mW/cm(3). This work constitutes the first demonstration of Fe3O4 as the conductive supports for Fe2O3 to address the concerns about its poor electronic and ionic transport.
authors.affiliation: School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China.|Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology , Nanjing 210094, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Tang
authors.affiliation: School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China.|Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology , Nanjing 210094, China.
authors.forename: Ruyue
authors.initials: R
authors.lastname: Jia
authors.affiliation: School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China.|Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology , Nanjing 210094, China.
authors.forename: Teng
authors.initials: T
authors.lastname: Zhai
authors.affiliation: School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China.|Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology , Nanjing 210094, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Xia
keywords: Fe2O3; Fe3O4; anode; asymmetric supercapacitors; core−shell; hierarchical