Construction of a hierarchical carbon coated Fe3O4 nanorod anode for 2.6 V aqueous asymmetric supercapacitors with ultrahigh energy density

Abstract

The low potential window and specific capacitances of aqueous asymmetric supercapacitors (ASCs) seriously restrict further improvement in energy density. Herein, a novel hierarchical nanowall structured carbon coated Fe₃O₄ nanorod growth on carbon cloth (CC/CW/Fe₃O₄@C) was fabricated as the anode. Benefitting from the ultrathin carbon protection layer and uniquely hierarchical structure, the CC/CW/Fe₃O₄@C anode exhibits an extended operating voltage from −1.3 to 0 V (vs. Ag/AgCl), significantly enhanced specific capacitance (463 F g⁻¹ at 1 A g⁻¹), remarkable rate capability (309 F g⁻¹ at 50 A g⁻¹) and superior cycle performance. To complement the wide potential anode, MnO₂ nanowire arrays were similarly prepared as the cathode (CC/CW/MnO₂) with outstanding capacitive performance. Remarkably, the assembled aqueous CC/CW/Fe₃O₄@C//CC/CW/MnO₂ ASCs operate in a stable and wide potential window of 2.6 V with an ultrahigh energy density of 91.1 W h kg⁻¹ along with extraordinary rate capability and cycle performance (92.8% retention after 10 000 cycles), surpassing most of the previously reported ASCs. This work provides a novel avenue to design and explore wide-voltage and high-capacity aqueous ASCs with further enhanced energy density.